engine problem on a 2000 cr vic

ok my engine does burn oil and I think its the piston rings but once in a while I hear this DING sound and a plume of smoke comes out of the tail pipe and the engine starts to have idling problems as if it wants to stall and sometimes it does. and this has been happening more often lately, was wondering what could cause this? are the piston rings getting so bad that the oil is getting way upthere where the spark plugs are and shutting them off? or is the the knocking/pre ignition everybody talks about(scanned the computer no codes regarding pre ignition) now I know I have pretty bad catalytic converters (still passed smog 3months ago) and a bad evap system I say this because the check engine light is on and the codes say it(P0420B, P0430, P1450B)but I really dont think these problems could be the cause of this. and btw how hard is it exactly to change piston rings on these cars..is it possible to do this without taking the engine out of the car. any help appreciated. thanks

I would first find out what the codes are. It also could be bad coil packs on the plugs, but I don't see that code comming up. How many miles on the car, and was it beat to start with?

thanks for the reply the fist two codes are for bad catalytic converters, which I just changed but the knocking problem still there. and the last code is for a bad evap system I am gona get around to fixing it this weekend but I dont see how it could be my evap system though!!