i bought a 1995 z28 with 97k miles for 5400. i first got the car and replaced the k&N. then a week alter i bought the K&N CAI. i noticed some better throttle response. my car has been acting sluggish, i think its the opti. at idle it bounces around about 50 rpms, but doesnt bounce at acceleration. last week i took off my muffler and it sounds awesome, but now i am noticing bad acceleration. is this the result of the muffler gone. or the opti? clogged cat? bad pistob ring seals?

 

anyone?

 

Do a tune up. Plugs, wires, coil, o2s, new cat.

 

Ditto...

Although I doubt you need another coil. Also before you buy a new cat check your current one and see if it's clogged. By nearly 100k it's quite possible and would definately point to your problems. If the car is on the original plugs/wires etc I'm sure that's probably it. If not, check for burnt wires and stuff.