What are the differences between the two? What kinds of gains will I see versus the stock one? Do I need a 60 mm TB to get the most benefit? The stock first gen B16a one is a 58, all I have done otherwise is I/H/E. Thanks.

bump

The USDM ITR uses a 62 mm (throttle plate) throttle body. The JDM ITR uses an even bigger throttle body (64 mm throttle plate if i recall correctly).

I read something about different IACV's not being interchangable, would the IACV and other parts off my first gen B16a manifold work?

If not, what car could I get an IACV from?

You can check part numbers for compatability here:

http://www.acuraparts247.com
http://www.slhondaparts.com