02 Back firing help please.

[8AVETTE]

My 2002 ACR has 400 miles on it and have just installed The headers, Hi flow cats and Corsa 3" and on the down shift and the Idle down in gear the car is back firing or popping

:mad It was doing this after I installed the new cats and Corsa also. Sounds bad. My 01 did not do this with the same setup. Any help would be great. Thanks, Don

 

[Steve-Indy]

...you mean.. " it sounds BAAAAAADDDDDDD!!!!" Our members pay BIG BUCKS for this result. On a serious note, check your plug wires.

 

[Gavin]

If it back fires just sitting idling - thats plug wires.
Backfiring on deceleration - check the collector gaskets - if they are leaking you will get nice backfire

 

[Craig 201 MPH]

that is a GOOD thing

 

[8AVETTE]

#1 plug was fouled, almost no gap.should have checked this first I gess.Still has some minor back firing but I think I may be normal. Thanks for the help.