When my car is sitting their ideling, it will back fire time to time, seems to me that to much fuel is getting out? where can i adjust the air fuel ratio? My mods are downpipe, maincat, catback, drop in KNN air filter with stock boost.

 

Hehe, mine does the same.

I believe the response I got was replace the o2 sensor, spark plugs or put in the pre-cat back in. =P.

Also tune it if you have a PFC.

 

You can't without a programmable ECU or other fuel management system.

How old are your spark plugs & wires, and O2 sensor?