Engine still lagging/bucking, help! Options

[GriffGirl]

I'm still having weird engine issues. It was bucking really bad until warm up, especially in higher RPMs. I did a tune-up which helped but didn't solve it, engine would still buck while cold at higher RPMs (3000+), and at about 3500+ when warmed up. Fiddled around some more this weekend, resulting in amazing improvement; now instead of bucking, it just kind of feels like it's dragging like a dog scraping its butt on the carpet. Yes, at higher RMPs, and regardless of what gear I'm in. I've done the following thusfar to resolve this issue:

•replaced thermostat
•replaced engine temp sensor
•replaced plugs, cap & rotor, air filter (improvement #1)
•replaced fuel filter
•seafoam gas treatment, seafoam vacuum line (discovered leak in gasket around header pipes)
•removed intake housing, cleaned the hell out of throttle body/plate
•realized that did nothing, REMOVED throttle body, discovered diamond mine in carbon deposits, cleaned thoroughly including all those tiny little vacuum tentacles
•whatever that thing is called (is it just the intake?) that the throttle body is attached to, well I sprayed the HELL out of it and soaked a rag too and did my best to clean it out. It looked like a stalactite cavern. Result was a marked increase in throttle response, made my car feel young again.

But still dragging ass on 3000+ RPMs regardless of gear. What is that thing the throttle body attaches to? Should I attempt to remove the cover from it so I can get rid of the rest of all that carbon build up? Is that my problem? Does anyone have any other ideas? PLEASE?

Thanks...

[Hanyo]

I had no idea there was a fuel filter in the gas tank. Where the hell is it and how do I get to it? And why haven't I ever heard of it before!? But yes, I did change the one under the hood. (Boy that sucked. The bottom nut was really really tight.)

The intank gas filter is that little white baggy in this picture:

its located under the rear seats. To replace it, you take the rear seats out and remove a couple of bolts and screws, unplug one or two wires and easy the fuel pump out of the gas tank. Its not hard to do, but remember to keep touching the metal car body to ground yourself and prevent static electricity.

If you've ever had a bad Cat, it will sound like something is rattling around in your exost pipe. and you'll hear it just with the little shaking you do when you get into the car.

generally the rattling is correct way to see if the cat is bad. But I've experience cats that are not fully clogged/broken.

But I do recomend changing your spark plug wires, it by far is the cheapest solution. If that does not help, my second guess would be the distributor. (i'm assuming your engine runs fine at idle and cruising).

Hmm... what did your old spark plugs look like? Was it black? Worn electrode? ect...