when and ONLY when the car is warmed up, and i give it more than 3/4ths throttle, the engine hesistates and actually shakes on the mounts as you rev it. sounds like its running off of 2 cilinders, this happens sometimes in on/off spurts, half a second good, half a second of hesisation... other times its from 4.5k rpms all the way to 6.5k rpms. it also happens sometimes when i come off the clutch from a stop. ive tryed everything, regrounded my MAF like the FSM says, yband'ed and tested fine, compression is exelent, no smoke of any kind even at 7k rpms....

any help is much appricated, i would think FPR or injectors but the yband tested fine, ive also ran injector cleaner through with no luck

Check the TPS, see if it smoothly rises and falls as you open and close the throttle. Check the inj's with a ohm meter.

Check you battery terminals for being loose or corroded...