Well, since you're on a limited budget, like the rest of us
, I'd start with the basics.
So do you have custom piping to your muffler, or is it just a muffler stuck on stock piping? If you like the muffler you have, go down to Midas and have them put on 2.25" piping for a few bucks; make sure its mandrel bent.
Next, I'd buy a high-flow cat, and stick that in, along with a new header.
Those will cost you a few bucks, so get those put on, and see if you like way things are going. You might decide that it is a deadend road to mod your F22 and you'll want to save up for an H22A.