Whoever thought it was a good idea to use those security torx bits on the IAC housing needs to have an "accident" happen to them. Ggrrrr!
For furure reference, the thread size on the IAC housing is M4x0.7-16
I used allen head replacements.
The throttle body itself is held on with M6x1.0-20
I used allen heads for those also.
My IAC took a lot of effort to remove and clean because there was almost 1/4" of carbon and crap in there... I had to scrape and spray and scrub with a toothbrush. It idles beautifully now and pulls smoother from the stoplights.