TPS Symptoms, not a bad TPS, thoughts, possibilities?

I have a 2001 5-speed 3.4 with cruise control (~220,000 miles), and about a year or 15 months ago the truck presented with a suite of symptoms that shouted TPS. All the typical stuff, including a CEL that came back with a TPS code. So, I replace the TPS with an aftermarket version. Good, symptom-free driving for about 12,000 miles, then back to the hesitation, etc., and another TPS code. My mechanic, who's a good dude that I've known for a long time and has worked on my trucks for a long time, thought that is was just a bad individual TPS (crappy Chinese manufacturing), so he warrantied the part, put on the same as a replacement, and sent me home. ~1,000 miles later, the same stuff again. This time, I ordered an OEM TPS from Toyota, replaced the Parts Plus one, and was good to go, or so I thought. This weekend, after maybe 800 miles on the OEM TPS, same stuff is back.

Thoughts? Is there a chance that the wire bundle could have a short in it? Is this bundle or wire assembly modular (meaning does it have plugs on either end and can be bought from Toyota)? Could it be replaced easily? I should also mention that my idle hasn't been normal since replacing the TPS the first time around. It tends to stick around 2000 even when out of gear, and generally seems kind of random. Could this all be caused by a bad Idle Air Control Valve? Should I drop $900 on a new OEM throttle body assembly and hope that fixes it? There aren't any vacuum leaks that I've been able to find, it only seems to present with these symptoms in 2nd, 3rd and 4th gear, not 5th, so highway driving has been okay. Can't imagine it's the fuel pump.

Anyway, I drive a lot for my job (lots of fieldwork in the middle of nowhere in the SW) and need to figure this out. The truck has been super reliable for the last 150,000 miles (since I bought it), and because it's a Toyota, I want it to get 300K +.

Any help at all or thoughts about this symptomology would be greatly appreciated.

THANKS!!!