I was under the impression that you have to use a stock wheel. I don't know if that means you can change them around at will based on all the different rims that there are, but I guess you could pick up some of the smallest steelies you could fit on those brakes. I race in street tire class so I'm out of the loop as far as R-comps go, sorry.
As far as the muffler, I don't know if I would spend any money there. I'm not sure welding a different muffler in would give you any measurable difference, and I don't know if they allow catback systems or not (still don't think you'd see much of a difference with all those cats, but I guess a catback would actually remove one so that's a no-no). If they make replacement high flow air filters for the 2.3 then see if you can grab one of those.
On shocks, someone correct me if I'm wrong but I seem to recall hearing how adjustables such as Koni yellows can be considered OEM replacements for stock class. You might want to look into those, as you can fine tune to match your driving.
It's been a while since I've read up on all the rules but I told you everything the way I remembered it. Good luck.
Yes, that is a banana in my pocket.
Dan - gump
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