Found the problem. Flowmasters are about the worst muffler for this engine. If you want something, look into Magnaflow or something like Borla or Corsa.
No, I found the problem
Originally Posted by mrbiggun1994
removed cat and rez and installed flowmaster 40's,
You should stick with the stock exhaust, unfortunately I have yet to find an exhaust that sounds good on a 3800.