A clogged cat is also what i was thinking, i had the same sort of issues in mine when the cat failed. I couldn't get above 3K and nothing above 60mph unless it was downhill. Easy way to check for a clogged cat (note -- DO NOT DO THIS ANY LONGER THAN REQUIRED -- exhaust gases are HOT when they're coming directly out of the manifolds. THINGS WILL MELT.) is to remove the upstream o2 sensor. Disconnect it so the PCM has to run with default tables for the sensor. If it runs up to redline without a problem, you've found your issue.
'94 Bonneville SLE | 266K miles
CAI - K&N cone filter - polished intake runners - 140 amp alternator - 2.5" exhaust - Magnaflow hi-flow cat - Magnaflow dual outlet muffler - 106K on engine and transmission - Sold 1/14/07
94 VW Jetta - 151K - 2.0 - 5 speed - Ghetto black steelie wheel mod - Techtonics 2.25" cat-back system