lean problem !!

[Asem]

hello everyone ..

i have lumina ss ( G8 ) 2007 manual .. its goes lean fuel .. and i retune it and after few days its go lean again :bang:
i change the fuel pump , sparks .. but i have a weak alternator in my car and some times it shows the buttery sing .. so my big Q is that effect on the AFR ?
also i got a bad number of HP its 366 with Full Bolt-Ons


any idea ?!

 

[SSVAGON]

Sounds to me you have oil ingestion in the inlet manifold which in return reduces the octane of the fuel.

Only way to really tell is pull off the throttle body and have a look inside see if there is any oil sitting inside the manifold.

Catch can is the cure.