It most certainly could be his TPS giving him idle problems. Can you describe the problem in a little more detail? 04DarkShadowGT is right about its location. You said you're having a problem with the TB/plenum install? If you have the stocker TB off it's only held on my two #2 bit screws.
Not to be a smart ass, but (jrc_03_GT) weren't you just telling someone else to "keep an eye on the A/F ratio" in another thread, but you can't even find your TPS...? How do you keep an eye on your A/F ratio?