what causes the sound you hear when you let off the gas and there is a rumbling sound like boomboom...boom....boom?

 

An exhaust leak can cause that. I blew a header gasket a couple of weeks ago and mine did that and it also made a real bad tapping noise.

 

theres no exhaust leak, you know when race cars let off the gas when going into turns and you see flames come out the exhaust some times and it makes a poping sound? thats what i'm talking about. my brothers 97 lt1 camaro does the same thing and its like new and has a flowmaster exhaust.

 

Just becuase it is a new exhaust does not eliminate exhaust leaks. If the gaskets and stuff not setting correct or if the bolts were not tightned down right it could have. If you have headers, check the bolts to make sure they are tight. If it's definatly not that maybe someone else can tell ya somethin else.

 

You could be running rich and burning the extra fuel in the exhaust system...

 

It's natural. Vacuum causes fuel to be drawn into the engine from the carb, it doesn't burn, it goes out the exhaust, some other cylinder eventually accidentally gets ignited, that one's exhaust flame sets off all the rest of the fuel that's been pumped into the exhaust. Normal. Watch a race on TV some time, especially a night race like at Bristol or Charlotte or Richmond, pay attention to the cars as they come into the corners. They're all doing it.

 

thought it was something like that but i wasn't sure exactly. thx, now i know.