Hello, I had recently switched out my test pipe and put my cat back in (the cat is in good condition) and since the switch my car has been sputtering during low rev loads and during idle. (sputtering with 2-3 second gaps in between) I took a shot in the dark and replaced the spark plugs (NGK laser plats) and I have no idea as to what to check next. Also, there is no check engine light. Any suggestions would be greatly appreciated. Thanks!

p.s. After the odd sputtering problem I had tried to put the test pipe back in but whether it's the test pipe or the cat the sputtering continues.

 

Exhaust Leak? Are you sure it is all tightened up correctly?

 

Hm, they were tightened pretty well and both gaskets have been replaced and sealed..

 

Oh and other than idle the sputtering only lasts till about 2-2.5k rpm, then it is smooth sailing after that point.