acutiy is supposed to net the most hp out of all the cai out there. i have one. its also the easiest to install as far as ive read.
i think i posted about someone on the hondata forum doing free tunes for people. im not sure how much i would trust a free tune, i mean people charge a decent amount to e tune why trust a free one? i dont know, thats just me. e-tunez.com is who i used. very knowledgeable, they will answer any questions you have through email even if you havent purchased anything from them. they offer a flat fee for the first tune then another $70ish to re tune for any simple bolt ons. for example. i tuned my car stock with a drop in k and n filter. the next year i installed the cai and down pipe and did a re tune for the $70ish. so when i eventually get my exhaust maybe next year, i'll probably spend the money for another re tune.
or you can just save all the parts and get one tune. you can absolutely do a stock tune, i noticed a night and day difference doing that. ive been tuned for 2 years now with no issues. also e-tunez is canadian! they do tunes for people all over the world ( maybe just north america? ).