I have a 1992 Buick Park Avenue with the 3800 series 1 NON supercharged V6. My car idles eratically when in park or drive. The rpm flucuates between 1100 and 600 then it will just die. I took it to the dealer four times for this and they cant find anything wrong with it. No error codes show up. I have replace the ignition system,IAC,PCV,vacuum house,O2 sensor,air filter, fuel filter. The dealer did say that my intake manifold gasket is leaking, but not enough to cause the car to die. I do also have a stage 1 Fastchip in car. If its not the intake gasket what could it be???