when my car is decelerating in gear, it makes like this burping/hiccuping feel and exhaust popping somewhat rapidly. it only does it when it gets to 3300rpm and under but above that its fine. any ideas what it could be?

 

Check all parts and settings related to your Anti-Afterburn system.

Get the Haynes manual and it discusses the procedure.
Check your BAC vavle
check your vaccum switch matrix at the top of the engine, and check/replace all your vaccum hoses that are the tinyest bit loose.

 

i had the tb mod done to it but took it off for certain reasons and replaced it with a tb i pulled from the jyard..could this have anything to do with it or on the tb i pulled? i replaced the thermowax block with my new one i had

 

hmmmmmm

Unknown.

You COULD sitch back to see if this problem goes away though....