my personal preferences for a cai, midpipe, catback and gears is as follows:
jlt cold air intake
any brand offroad x pipe, not much difference between them all
borla s-type catback
frpp 4.10 or 4.30 gears. 3.73s don't do a 4v justice.
I thought about doing 3.73's but they really arent much of a jump from the 3.55. I got myself a xpipe now I just need a catback to finish the exhaust. Is the CAI better than a RAI?
i have no personal experience with mach 1s, but from searching various forums many a enthusiast prefer the jlt rai > jlt cai. but jlt is definitely the way to go. they provide the most rwhp in most cases, as would be the case with your lightly modded mach 1. and don't waste your time with 3.73s in a 4v. 4.10s+ is the way to go, your car likes high rpm, and that's what a numerically higher gears like to do, spin to high rpm quicker.
you'll also need headers to complete the exhaust, longtubes for more power.