Once your aftermarket throttle body has a sealed in IAC system (as per the previous page's "self explanitory pictures") like the GM factory engineers intended... you then simply drill a hole (like shown in the pictures).... I personally always start with a very conservative size hole, using a 1/8th drill bit, (which is about the same size as the hole on the Stock GM LT1/LT4 throttle body's that came on the performance oriented vehicles)..... IME, (especially if you have a decent size cam) Most of the time, you will still need to go larger from that conservitive 1/8th size hole starting point..... How large you will need to go depends heavily on your particular engines modifications, Vehicle weight, Transmission type, Ect...Ect... (trial and error baby,lol)..... In my experience, it is VERY common to end up needing a hole "just at" (or even slightly over) 1/4 inch in diameter, "especially" on Automatic transmission cars running Pretty big cammed engine set-ups with Narrow LSA's (IE: lots of overlap)...................... THROTTLE BODY "ON CAR SET-UP":  Once the new Throttle-Body (and TB Gasket) is verified to be aligned correctly (IE: TB bores lined up "perfectly" to the intake manifold bores without ANY mismatches or ledges of any kind) and bolted in place.....Reset your IAC valve (as per the factory RE-set method)..... Turn the throttle-blade adjustment screw (on the drivers side of your TB) until your throttle blades just start to open..... Adjust your throttle cable (as per the factory method for your year and model car) making certain that your getting a 100% FULL throttle when floored (IE: throttle blades verified to be all the way open)..... Also, I personally ALWAYS slot out the mounting holes on the (TPS) throttle position sensor so that it can be "easily" adjusted (IE:rotated) for a precise setting.... Here's a link from GOLEN ENGINES about slotting and adjusting the TPS sensor (and the TB throttle-blades) http://www.golenengineservice.com/html/tps.html   ....Then start, and test drive the car to check all of it's idle, off-idle, and driving characteristics..... Make sure to do "several" 20-30 MPH coasting type stops(just normal type stops like your coming up to a red light)...... Cammed cars, "especially" behind automatic transmissions have a strong tendency to need an even larger IAC hole size (as previously mentioned) to alleviate a "Near stall", or a super low "idle-drop" condition that can be VERY bothersome during stops like the ones mentioned (some guys i've seen are willing to "completely" change their driving style to a two-foot method when coming to stops (IE: gas/brake) to deal with this kind of crap, "I  Am  Not",  LOL....... You can also, get the car on a scanner, and vary the IAC hole size (and throttle blade angle) to get your IAC counts between 25-40 to try to get it closer as a starting point.... Myself, I personally prefer to rely more on the test-driving and tuning method , rather than to live and die by the scanner, but that's just my preference and what I got used to over the years....... Obviously, this can all take a bit of time messing around to get it just right, but it's well worth it in the end if you are wanting to achieve a "near stock" type drivability out of your car.