Running problem I've streetfightered my zx9r b2 and made a 4 into 2 exhaust system. But without blocking half the air intake it will only do 40mph. even with the air intake blocked it splutters at 6,500rpm. how can i solve this problem?

If the fuel system is free flowing with no restrictions then you may be having a problem with your exhaust system. When catalytic converters get hot they block the exhaust and it backs up into the intake area. Since exhaust can't get out, air can't get in and fuel isn't drawn into the engine.

A plugged muffler or other restriction can also have a similar effect.

Based on the facts supplied, there could be various possible causes for the Rover 75 petrol 2003 problem. Here are a few plausible explanations for why the car starts, runs briefly, and then stops:

Fuel Delivery Problem: Even when the fuel pump and injectors have been inspected and determined to be in good working order, there may still be a problem with fuel delivery. It could be a blocked fuel filter or a faulty fuel pressure regulator.

Problem with the Ignition System: The problem could be with the ignition system, such as a faulty ignition coil or a malfunctioning crankshaft position sensor. These components are in charge of creating the spark needed to ignite the fuel-air mixture in the engine.

Electrical issue: An electrical issue could be hurting the engine's performance. This could be due to a malfunctioning sensor, a loose connection, or an issue with the engine control unit (ECU).

Blockage in the air intake or exhaust system: A limitation in the air intake or exhaust system might cause the engine to malfunction. Check the air filter, intake manifold and exhaust system for any obstructions.

Possible plugged catalytic converter ! is the check engine light on ? You should take it an have scan tool hooked up to see if any codes are stored in any control modules ! An have exhaust system pressure tested !

crank sensor would be my next bet. 40 mph is safety mode to not damage the engine. i.e get home mode.

sounds like you may have a plugged up exhaust or catalytic converter. Try removing the o2 sensors from exhaust pipes and see if it runs better. If it was a timing issue it would idle bad.

check the thermostate. it may be opening late.
Check the cooling system and may be you need a good bleeding of air from the system.Hope this helps!

Could be.
Has the thermostat been replaced ?
You could run the engine without the radiator cap to see if the system has air pockets.
A restriction in the exhaust could cause the engine to run hotter on the road than on short trips.

The bolts should have thread lock on them when installing, and the torque is done in 2 steps. 33 ft lbs. and then 90 deg. after that on the second pass. 3.1L Engine CAUTION
Observe all applicable safety precautions when working around fuel. Whenever servicing the fuel system, always work in a well ventilated area. Do not allow fuel spray or vapors to come in contact with a spark or open flame. Keep a dry chemical fire extinguisher near the work area. Always keep fuel in a container specifically designed for fuel storage; also, always properly seal fuel containers to avoid the possibility of fire or explosion. LEFT SIDE (FRONT)

1. Properly relieve the fuel system pressure.
2. Disconnect the negative battery cable.
3. Drain the cooling system into a suitable container.
4. Disconnect the top half of the air cleaner assembly, then remove the throttle body air inlet duct.
5. Remove the exhaust crossover pipe heat shield and crossover pipe.
6. Disconnect the spark plug wires from spark plugs and looms then route the wires out of the way.
7. Remove the rocker arm (valve) covers.
8. Remove upper intake plenum and lower intake manifold.
9. Remove the left side exhaust manifold.
10. Remove oil level indicator tube. NOTE: When removing the valve train components they must be kept in order for installation in the same locations they were removed from.
    
11. Remove rocker arms nut, rocker arms, balls and pushrods.
12. Unfasten the cylinder head bolts evenly, then remove the cylinder head from the engine compartment. Remove and discard the gasket. To install:
    
13. Clean all the gasket surfaces completely. Clean the threads on the cylinder head bolts and block threads.
14. Place the cylinder head gasket in position over the dowel pins on the cylinder block so the words THIS SIDE UP are showing.
15. Coat the bolt threads lightly with sealer, then install finger-tight.
16. Tighten the cylinder head bolts in sequence to 33 ft. lbs. (45 Nm). With all the bolts tightened make a second pass tightening all the bolts an additional 90°.
17. Install the pushrods, rocker arms, balls and rocker arm nuts in their proper locations. Tighten the rocker arm nuts to 18 ft. lbs. (25 Nm).
18. Install the lower intake manifold and upper intake plenum.
19. Install the rocker arm (valve) covers.
20. Install the oil level indicator tube. Insert the dipstick.
21. Connect the spark plug wires to spark plugs and looms.
22. Install the left side exhaust manifold.
23. Install the exhaust crossover pipe and heat shield.
24. Refill the cooling system.
25. Install the top half of the air cleaner assembly and the throttle body air inlet duct.
26. Connect negative battery cable.
27. Start vehicle and verify that there are no leaks. Fig. 20: Cylinder head mounting and bolt tightening sequence - 3.1L engine
    

RIGHT CYLINDER HEAD (REAR) CAUTION
Fuel Injection systems remain under pressure, even after the engine has been turned OFF. The fuel system pressure must be relieved before disconnecting any fuel lines. Failure to do so may result in fire and/or personal injury.

1. Relieve the fuel system pressure.
2. Disconnect the negative battery cable.
3. Drain the cooling system.
4. Remove the top half of the air cleaner assembly and remove the throttle body air inlet duct.
5. Remove the exhaust crossover pipe heat shield and crossover pipe.
6. Raise and safely support the vehicle.
7. Detach the Oxygen (O2) sensor connector.
8. Disconnect the exhaust pipe from the exhaust manifold.
9. Remove the right side exhaust manifold.
10. Carefully lower the vehicle.
11. Disconnect the spark plug wires from spark plugs and wire looms and route the wires out of the way.
12. Remove the rocker arm (valve) covers.
13. Remove upper intake plenum and lower intake manifold. NOTE: When removing the valve train components they must be kept in order for installation in the same locations they were removed from.
    
14. Remove rocker arms nut, rocker arms, balls and pushrods.
15. Unfasten the cylinder head bolts evenly, then remove the cylinder head from the engine compartment. Remove and discard the gasket. To Install:
    
16. Clean all the gasket surfaces completely. Clean the threads on the cylinder head bolts and block threads.
17. Place the cylinder head gasket in position over the dowel pins on the cylinder block so the words THIS SIDE UP showing.
18. Coat the bolt threads lightly with sealer, then install finger-tight.
19. Tighten the cylinder head bolts in sequence to 33 ft. lbs. (45 Nm). With all the bolts tightened make a second pass tightening all the bolts an additional 90°.
20. Install the pushrods loosely retained with the rocker arm assemblies. Make sure all pushrods are in the correct locations. Coat the ends of the pushrods with prelube. The intake rods are marked yellow and are 5 3?4 inch long. The exhaust pushrods are marked green and 6 inches long. balls and rocker arm nuts. Tighten the rocker arm nuts to 18 ft. lbs. (25 Nm).
21. Install the lower intake manifold and upper intake plenum.
22. Install the rocker arm (valve) covers.
23. Connect the spark plug wires to spark plugs and wire looms.
24. Raise and safely support the vehicle.
25. Install the exhaust manifold.
26. Connect the exhaust pipe to the exhaust manifold.
27. Carefully lower the vehicle.
28. Connect the Oxygen (O2) sensor wiring.
29. Install the exhaust crossover pipe and heat shield.
30. Refill the cooling system.
31. Install the top half of the air cleaner assembly and the throttle body air inlet duct.
32. Connect negative battery cable.
33. Start vehicle and verify that there are no leaks.

check up and clean the half turbo system and in this case need to block the communicating hole between the turbo charger and air intake exhaust and barometric sensor

You have a vacumm hose loose look for small hose no connecter to anything - should solve it - I had a similar problem with a ZX9r the other day - same would run fine on choke not idle or start without it

Good Luck

Del