It could be anything. Bypassing a sensor does not guarantee that its the sensor's fault. If you remove a sensor, the computer will run in a different looping mode and will operate at lower potential, but it will at least operate. On my MR2, I had a bad knock sensor so I just unplugged it and it ran better with it unplugged, but it would run very rich because it prevented full ignition advance and the power was just par. So at that stage, I could have unplugged my o2 sensor, my tps sensor, my engine temp sensor, and I bet that with simply knowing the engine rpm and the manifold pressure (as my engine uses a MAP sensor) it would still turn on and operate as long as it was mechanically ok (timing was set, valves are adjusted correctly, cam timing is correct, ignitor was working ok, etc)...
With that said, of course the easiest way to check if it is the TPS is to swap in a good one. First I would check for codes, if there are no codes then I would swap in a different TPS and see how it responds to that, and hopefully it really is the TPS sensor; best case scenario.
BigMike
