I have a 96 gt which has mac long tube headers,flowmstwer mufflers, JLT rai, 3.73s and will have pi intake/ pi cams in a week or two. How much of an improvement will I see with a custm xcal2 tune?
You should be pleased with the results, you will pick up decent power. But the real benefit will be better driveability - if the place you get it from customizes it for the cams and long tubes like we do. Not doing the heads now will keep you from getting the most power out of it, but it's more affordable to do it a little at a time - you could get one of the 3 tunes for the PI heads and then when/if you ever do them, the tune will be there and be correct for them.