Alright this is whats going on. I have an 03 cavy with a 06 cobalt swap. The problem is that when you get on it, it will bog out and you have to shut it off and turn it back on. Sometimes it will bog out so bad that it jerks the whole car and you almost hit you head on the dash/steering wheel. Had the codes read it say random miss fire and a bad caty. Can a bad cat really do that much? No idea where the miss fire is coming from.


2.2 ecotec (stock internals) typhoon k&n in take 2 inch drop springs

There are some great, knowledgeable (much more so than me), helpful people on this forum who hopefully will help you, but since nobody has answered yet, I'll toss this out, just in case it helps.

I have two 1996 Cavaliers (2.4L) which employ a coil-over-plug ignition system. On both cars, the ignition coil housing (and probably the coils) failed, which eventually caused them to misfire. I replaced the ignition coil housing (and the coils, boots, & plugs) for $78, which solved the problem. You can read about it here.
http://www.j-body.org/forums/read.php?f=11&i=165871&t=165871

I don't know if your car has a coil-over-plug ignition system, but if so, you may want to consider changing it out. My car did throw a code about misfiring, but nothing about the catalytic converter. Perhaps beacause the car is misfiring, the un-ignited gas vapor is overwhelming and confusing the catalytic converter and/or related sensors. I dont know. Good luck!