It'd be good if you could describe exactly what the config of the car is first for us, and add some descriptive photos, happy to lend any help I can to you.
TPS may be faulty or not calibrated well. Also, have you got all the facilities of the efi system connected properly, knock sensor, icv, the lot? If its running pretty smooth and still gutless, it may be running in a trimmed safe mode, which it will default to when a sensor dies or is not present. Perhaps find someone with the same motor and swap sensors one at a time and evaluate the change. Has the manual above been of any use?
Id say photos would be handy. Reach under the quads and flash one off, there is vacuum stuff under there which needs attention sometimes, and id like to see whats up with the icv and the knock sensor. If it were a simple vacuum leak or something like that it would be fine under load in most circumstances, but shit at idle.
Yeah definitely need pics.