Mind BogglingProblem with 1990 GT Celica Master Troubleshooters inside please.

I have a 1990 Celica GT 5 speed. 130k miles. Just purchased it for a great price, Red, coupe, power everything, sunroof, shiny red paint and no accidents. Anyway, many people have worked on it. The problem is that the car has a major surge/studder at about 2000-3000 rpm, in neutral you step on the gas, rpm's rise to about 2000 it hesitates, then pops up to 3000 and flys up. It does it in all the gears, except when im on the freeway at 80+mph. It jerks violently at times at thoes RPM's. It seems to idle normal, with a slight rumble.

Items replaced:
Distributor
Cap
Rotor
Coil
Plugs/wires
Throttle Position Sensor
3 Carbon deposit cleanings
Different ECU from a donor vehicle
Valve job
o2 sensors

This is from speaking with the owner. No CHeck engine light, no codes to pull. Its bascially a guessing game.

My previous experience with my 2002 nissan maxima, the hesistaion/jerking was extrmely similar to removing hte Nissan's Mass Air Flow sensor. Causing it not to know how much air is in the system, making the car run retarded.

Now, any ideas out there? What to check? What to replace? Not sure if its simple or not. I know there isnt a MAF sensor.....is it a MAP system?

THanks for the time you took to read my post.
Larry

Forgot to mention Timing belt. ALso the problem got gradually worse. It started at some random time...and got worse. =)