Custom 88 has the aftermarket Maf installed. And likes it the last I heard. The controller is a bit of change and definately not worth the money unless your going to nitrous(
) or turbocharge. I went 75Hp wet nitrous injection and love the spankings I hand out.......when I can keep a license.
Is your GXP new? The N*"* really loosen up nicely as you put some miles on them, and running premium really makes a performance difference. The K&N drop in filter will probably give ya as much as either of the two items you mentioned. Check out Squires STS Turbo systems when you have a chance for a wish list. They should have something other than a generic fit all kit for the Northstar before to long