Sorry for bringing back an old thread, but I've been doign some experimenting
Originally posted by DemonSVT:
There is absolutely zero power loss from the TH fix. There couldn't be because the IAC is closed when the TPS signal is not at rest.
This is what really had me thinking. You see, in my experience, there is absolutely beyond a doubt a difference in performance with the TH fix. Its what we define as "performance loss" that I think is confusing.
If the IAC is closed at WOT, this makes sense that at WOT there would not be a performance difference. And that I agree with; that even with a TH plug in there, at WOT, performance is the same. However, I theorize that the sluggish performance we experience is a loss of throttle response at steady speeds and around town driving. That first tip-in of the throttle when cruising is noticably more sluggish with a copper cap and small hole (small being 5/32" 3/16" or so).
My methodology of testing began with a 5/32" hole in a copper cap and I've increased the size of that hole by 1/32" with each test. I would install the cap, go for test drive of about 10 miles mixing city and highway driving. With each cap that was larger I noticed better throttle response each time. I'm now up to 5/16" and have no moose yet and the car feels the best it has since I started testing.
I might add that don't really have problems with throttle hang (mostly due to the ADC tune I have) but since I installed the headers the car began moosing very badly so I turned to the "TH Fix" for a fix but I immediately noticed the car feeling very sluggish and I began testing larger holes. 
