In short, if you can't afford a tune...
Maybe you should spend the cash on suspension/brakes or other mods.
On the flip side, if you want MAX gains for MIN cost, buy a berk or nameless muffler delete (Check the thread here
http://www.ft86club.com/forums/showthread.php?t=22727 to see the berk muffler delete that cost $150 dyno more than any other cat-back tested) , and a drop in filter ($50) - that should cost you $200. Spend the $800 you save... ON A TUNE!!!