Shaving the heads a little wouldn't hurt. The stock compression ratio is so low that anything you can pick up is worth the effort. Head milling is pretty cheap assuming you don't get carried away and have to start angle-milling, fly-cutting or machining the intake.
Definitely spring for some larger injectors. This is where the Mass Air system would benefit you. More tuning options IMHO. You could upgrade the MAS and injectors. Pro-M has a sweet new 80mm unit.
Also, you don't say what you've done for exhaust. If you've still got the cats on your H-pipe, dump 'em. Go 2 1/2" all the way back through some free-flowing mufflers. I prefer the Flowmaster 2-chambers.
Shed weight in the beast wherever you can and stiffen the chassis with some weld-in subframe connectors. If you're running on slicks often, then bullet-proof the rearend with cap studs, a girdle and some Moser axles w/ long studs.
Ahhhhh. So much to do, so little time and money.
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Jeff Chambers
T/S #4
12.40 Seconds/109.5 MPH
http://www.kellnet.com/chambers/default.htm