My 95 4 door sidekick (160,000 miles) all of a sudden appears to have lost power.  Idles and runs fine. Recent tune up and fuel filter change (about 3000 miles ago).  I have a hard time getting it to get over 3000 rpms?  Could it be a clogged cat?  I'm in Oregon and considering taking it out, with an exhaust upgrade.  Any thing else to look at?  It usually runs like a raped ape, but now something is definitely wrong.

Sometimes the bolt comes loose on the distributor, and allows it to move. Could be a lot of things. Can you describe the problem anymore?

No stutter, skip or hop.  Starts, idles and appears to accelorate like normal.  Usually in 4th or 5th gear I have no problem gaining RPM's.  Now once in 4th and 5th gear on level ground, with the petal mashed to the floor I have a hard time getting it to 3000 rpm.  Even in fourth it takes it twice as long to gain RPMs.  It almost feels like it is not breathing.  It reminded me of an old dirt bike I had back in high school that ran like crap until I figured out it had a spark arrestor in the pipe that was completely gummed up. Need to fart around tonight and look at some stuff.  Really just noticed it today on my 20 mile drive to work.  As I don't have to worry about smog stuff around here, I was wondering about rooting out the cat.  I'm new to the zuki and any help would be greatly appreciated.  I'm having a hard time finding words to explain the difference / change in performance over the past couple days but know something is not right.

I hate SMOG and hippies equally, but the cat does do the environment good. If you can avoid it, please don't hollow out the cat. Check your timing (the exact same thing you're describing happened to me, it was a loose disty bolt), and shake the muffler. Usually if the cat's starting to blow out, and clog things up, you'll hear things rattling in the muffler. Take a good look under the hood and see if anything's been accidentally unplugged, or looks loose. If it's running "normalish", no smoke coming out the rear, no sludge in the oil or anything, I'd doubt it's a blown head gasket... but it could be. Could also be a failing fuel pump, clogged fuel filter, or something not right in the carb.

Thanks Jeremiah,
I'll take a look at the dist. tonight along with some other stuff.  I too worried about head gasket, but I'm not seeing the signs so far. I live at 5000 elevation.  I guess I need to ask or find some timing recommendations if anyone has them.