I have a 1997 Cavalier, 2.2l, automatic. I've had the vehicle for about a year, bought it with about 100,000 miles. It now has 130,000 miles and has always idled a little rough, but always did just fine. However a few days ago the started idling rougher than usual and will not go above 40 MPH now. The idle surges now (fast surge, sounds like a rurr, rurr, rurr, rurr, then settles down and sounds normal, then races again). Here's what I've done:

CEL indicated misfire, TPS, MAP.

Replaced plugs, wires, TPS, MAP sensor, IAC, air filter, cleared CEL. Checked fuel pump pressure.
Misfire came back once, cleared it, has not come back.
Car idles slightly better, still races (rurr, rurr, rurr, rurr, then settles, then does it again, then settles, etc), but still no power. Power feels decent until about 2500-3000 RPMS then the motor feels bogged down. Pedal to the floor gets me pretty normal acceleration, then the power feels like it complete drops out. Max speed is about 40 MPH (and it takes forever to get there).

Any ideas? I'm thinking it could be a clogged catalytic converter, jumped timing chain, or clogged injectors, but I'm hoping some j-body gurus have seen something like this before.

Vacuum leak?Transmission not shifting right?Trans fluid level not correct?Fuel filter,Fuel pump,Fuel pressure regulator?Timing chain stretched out?Do a compression check.Restricted exhaust?I always make a troubleshooting check list.

Sounds like a clogged up Cat.... usually you'll get a sulfurous smell under load... of course it could be any of the others mentioned above

Just my 2 cents!