it's not always bout the gains tho....sometimes it's just bout makin it your own an havin fun doin it ::shrug:: sure, there's things that we could do instead....an you know that we're not doin it to up the resale value
he asked what the best performance mod was....not if you thought that he should mod it
if you're lookin to spend some money then definitely go FI...nitrous ain't always as safe as everyone thinks it is. NA is good an probably a little more reliable....but for the extra money it costs, you won't get as much gains as FI

either way, make sure you read a lot of the threads in the related forums here on PO before jumpin into it too soon.