I am perplexed! My truck is running really, really, rough. It doesn't seem to have any pattern, except, it seems to run ok in the morning, or when cool. Shortly thereafter, begins to surge.
Ok by rough I mean:
-Noticable decrease in power and fuel economy
-Motor seems to "surge", feels as if I hit a speed bump when motor surges.
-No particular RPM range, pretty much all the time.
-Exhaust seems to get deeper, or louder when running rough.

YEAR: 1990
MOTOR: 2.9L V6
TRANNY: AUTO
DRIVETRAIN: 2WD

 

Sure sounds like cat converter may be clogged to me, this gets worse when hot and may be backing exhaust up and leaking at manifold to y pipe connection and causing it to get louder. Simple test: If you have o2 sensor in front of converter, just remove it and see if you have a noticable power increase.

 

Do you have a CEL light? Do a KOEO and KOER test. You might find a bad component like a throttle position sensor or something. I had a 94 4.0L that was doing something similar to yours and I had no CEL. After the tests, I found a bad tps.