ok , so i have an 88 lo3 i have a exhaust leak and as i have heard eshaut leaks make cars run richer . so my bird is running rich due to that . , well i started her up today and while in idle i reved it up a bit not even over 2000 rpm's and i was looking at my tbi unit and it back fired , " its like it sneezed" , it was a short rev , after that i didnt want to mess with it , could running rich make this happen ? or what else could cause this , timing , anything would help .

 

An exhaust leak wont cause a rich condition by its self, the only way it will cause it is if it is close enough to the O2 sensor that the leak is causing extra O2 to get into the exhaust, that causes the sensor to read lean and the PCM to start injecting more fuel cause it thinks its lean.

 

so the leak would be where the headers meet the heads ? what else could cause rich condition ?