I have an air leak in intake line - Hayward SAND FILTER, PRO SERIES

Yeah, about ten times better. Look, you need vacuum in the intake manifold, you have to have it or air wouldn't rush in from the air cleaner, the engine would not breathe, and it would sit there and barely run, or not run at all.
By design, vacuum is created when the piston in a cylinder is pulled down by the crankshaft and the intake valve is open. So air from the intake moves into the cylinder, leaving a vacuum (lower air pressure) in the intake manifold. For more air to be drawn in, but it's a set amount of air. Vacuum leaks and leaking intake manifold gaskets pull in extra air and lean out the air/fuel mixture too much. So plug off that hole and make sure no vacuum leaks.
For your '72, an inexpensive vacuum gauge would be a wise investment. Check this site for its usefulness:
http://www.secondchancegarage.com/public/186.cfm

All engines run with a vacuum in the intake, a good engine should have a steady vacuum of between17 and 21 inches on the gauge at idle. The tighter and less worn the engine is, the vacuum will be higher, like 21 inches Hg. But should be at least 16 or 17, and steady. Learn how to use a vacuum gauge and you can tell a lot about the engine's condition-just check the site.

sounds like a coil problem to me

You have to find the leak and seal it up, hey. It may help to picture where vacuum originates in the engine: As the pistons move down in the cylinders they pull air in from the intake manifold. This creates a pressure drop in the intake, a vacuum that is maintained as the engine is running. New air that is pulled into the intake is measured by the Mass Air Flow sensor mounted in the big boot between the air filter and the intake. If extra air is pulled into the intake manifold from a vacuum leak, uncalibrated air, the computer can figure it out from the oxygen sensors reading in the exhaust-mixture is too lean, so the computer will try to compensate by delivering more fuel, but can't deliver enough, mix is still too lean, so computer sets a code for the vacuum leak.
The intake will have a few vacuum taps with hoses running to engine or car controls that require vacuum to operate. If one of the hoses comes off or has a leak, that is extra air into the intake. Your power brake booster has a large vacuum tap. That may be the problem. With the engine running, pull off that line and plug it, and see if engine speed changes. If the idle drops that may be your leak-a failed power brake booster.
If nothing yet, keep engine running and spray some starting fluid around the mounting area of the intake manifold (maybe the intake gasket has failed and sprung a leak) and listen for a change in engine pitch or speed. The fluid may get sucked into the intake and cause speed to change. If it does, you would need to remove the intake manifold and fit a new manifold gasket.
Also check the big boot from the air filter to the throttle body for tears or loose fit. Good luck, Rev!

intake manifoold leak check all vacuum lines replace all vacuum lines if look cracked ,spark plugs could be fouled out by leaking fuel injectors, clean fuel injectors,replace fuel filter,replace air filter,replace spark plugs and wires,do tune up see if it helps if not.could have leaking intake manifold gasket or leaking egr valve,use engine vacuum gauge check engine vacuum for intake manifold gasket leaks.

various problems but mostly i find idle surging and droping over and ove r is a vaccume leak, or an intake leake somewhere, such as in the air filter housing, air intake tube, or at intake to manifold seal. check vacumm lines, air filter ect. fuel filter replacement wouldnt hurt, is there a check engine lite?

I think you have an air leak, a vacuum line loose, or possible intake manifold gasket leaking, maybe your big air intake hose is leaking. spray carb cleaner or soapy water around mating surface of intake and on vacuum lines and connections. If idle changes, there is your leak. good luck.

Whistle noise indicates a major vacuum leak. Maybe something loose in the intake system. Maybe a vacuum hose disconnected. Will explain lose of power also.

You could have either an injector that is stuck open or a fuel pressure regulator that has developed a leak. A leaky injector will usually only leak fuel into one cylinder as it is located just above the intake valve in the lower part of the intake while a leaky fuel pressure regulator will leak fuel into the front end of the intake manifold [behind the throttle plates] and the fuel will acuumulate throughout the upper intake plenum. When a fuel pressure regulator develops a leak the fuel that is escaping from it flows through the small 1/8" diameter plastic vacuum line which goes from the top of the regulator to the intake manifold. Even a trace of fuel in this line means the regulator is bad. I've seen both leak items leak but probably replace 10 regulators leak for every one injector. Good luck, hope you find your problem!

You could have either a vacuum line leak or an intake gasket leak. Often an intake gasket leak will also cause an oil consumption issue as the actual vacuum leak is at the bottom side of the intake and will result in not ony a misfire at idle but will pull engine oil into the intake causing a loss of engine oil. The other primary sources of leaks I find are broken plastic vacuum lines, usually on the passenger or rear side of the engine. The throttle plates on these do cause a loud hissing noise [normal] so it's often hard to pinpoint an actual vacuum leak unless the air cleaner is on which mutes some of the normal air noise.

I assume it is a turbo diesel? Then:

Location of the sensor:
- in early cars is in the ECU, with vacuum pipe going from intake maniforld duct to the ECU
- later models on the air intake duct, with wiring going to the ECU.

The fault may often be caused by:

- air leaks in MAP sensor line to the ECU (early ones only) or any of the vacuum control line hoses. This normally due to perished/loose flexi pipes, etc).
- leaks in the air hoses going between turbo/engine/intercooler. Can be spotted by slight oil contamination at the point of leak.

Or it's variable vaine sticking (even intermittently) in the turbo due to contamination, preventing the turbo from performing according to the ECU demand, and hence being 'shut-off' by th ECU

So - check all vacum line for leaks, ensure turbo actuator is free to move, all air hoses are intact and secure, intercooler not leaking.