Audii-Dudii

but is it possible to swap the _chips_ themselves from one type of ECU to another or are all they all different? Every aftermarket chip vendor I've checked seems to lump all the different boxes under the same part number, although this doesn't necessarily mean the chip or the code contained therein are interchangeable.

I know I've publicly said that I didn't plan to modify my car, but I have an "M" box spare (thanks, Rob O!) that can be swapped for the "T" box in my '02 and someone who works in my building (and jumped ship to an M5 last year as the maintenance and repair costs for their '01 S4 started to climb) offered me a dead "H" box that has an aftermarket chip installed (to the best of their recollection, it's a GIAC, which seems logical as they had EVO Motorsports do some work for them and they're a GIAC dealer) in exchange for buying them lunch and a few beers someday.

If can get away with just swapping chips -- in a past life, I was an electronics hobbyist so I am fairly confident I can do the job myself -- for next to no money, this opportunity strikes me as an omen that I would be foolish to ignore! (Yes, I know I could simply take the box and then sell it on eBay and use those funds to defray the cost of having a chip installed in my ECU, but without going into details, it would be office diplomacy suicide if I was ever found out and I've learned the world is smaller than you think at times...)

Ochlockonee

You may be able to swap between boxes that use the hitachi maf. I don't know.