That's about it. Unless its an item that will normally wear out (and wouldn't normally improve performance) assume that you can't change it. If its internal to the engine, assume that its got to be OEM parts. If its emissions related, its got to be OEM.
I almost forgot... you can do anything the Factory Service Manual allows. If the FSM allows an overbore, you can do that. You can balance the engine using factory parts that are all within tolerances specified in the FSM, etc. But now we're talking about large amounts of money for 5 or 10hp.
You could replace your stock wheels, with the same dimension wheels (16x7) except in an ultralight (and ultra-expensive) variety. That'd help your acceleration by eliminating rotating weight, but that's getting pretty esoteric.
Basically, you're pretty close to the limit of what you can do (power wise) legally and remain in Stock class. That's why they call it stock, after all. Pretty much the only things you can change are items that normally wear out.
Spend your money on some good shocks and some R-compound tires (if you haven't already) those are the two biggest things you can do to the car in Stock to go faster.