2000 Lexus GS300 I have codes po300 po302, po303, po304, po305, po306,po171

all misfires and bad mixture of fuel and air

https://www.google.com/search?q=05+TAURUS+CODE+SHOWING+po171+po174+po300+pO303+pO304

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YES, you have to investigate what is throwing your valve timing off. That could be anything from a vacuum leak to clogged injectors, bad plugs, sensor ect. Have the car analyzed to find the cause. There can be many causes. Good luck

Do tune up,coils module,wires,plugs and see what happened..

PO300 and P1399 are random cylinder misfire detected.
PO301 cylinder 1 misfire
PO302 cylinder 2 misfire
PO304 cylinder 4 misfire
PO306 cylinder 6 misfire
I would say that you have damage to the ignition wiring harness or you ECM is failing.

I've had similar issues. The fix I used was to take my vehicle to AAMCO and let them run a diagnostic check. Most often it will be at little or no cost and, if you don't want to mess with the fix anymore, they can fix it onsite.

If a tune up (spark plugs, ignition wires, distributor cap/rotor button or coil packs) don't work, try checking the fuel system.

Sounds like you still have air leak.

code p0335

Hi these are mis-fire codes ,
P0300 is a general mis-fire detected code the others relate to specific cylinders,
P0302 is cylinder 2 misfire
P0303................3........
p0305..................5........
I would check your spark plugs first if Ok you need to make sure the coils are working ok for this you need an osciloscope to check output voltage if your not sure then take to a qualified mechanic with Cadilac experience it could be caused by an air leak,bad ECT sensor or even Mass air flow sensor ,codes only tell you the result not the cause

might be the coil pack is bad, wires, plugs, o2 sensors, dirty injectors, catalic converter ( only if you smell rotten eggs ) . cylinders are misfireing.