the.main.man

Looking for some input....
1) Spark plugs....I picked up Spitfire Platinums today just cause I was at the store.....Aside from the over-hype any opinions?
2) Fuel rails - is there any benefit to changing out the stock rails on a N/A GT? Should I also change the fuel regulator as well?
3) Gears....Everyone seems to indicate that gears are the way to go and I'm seriously thinking 3.73.. I do about a 50/50 mix of cty/hwy.....I hear that the Ford Racing gears are better (??), also is this a job that I can do myself? I don't know who to trust to have them done around me....
4) Should I invest in a Diablo or another "programmer"? My specs are on the sig.....what kind of return will I see for the cash layout?
5) Thermostat? I again hear that I should get a thermo with a lower temp threshold? What brand/temp should I look for?

Cheers!

_UnLiMiTeD_

gears is a must have mod for these cars. Most will tell you 4.10 but if you do a fair bit of highway driven i would say 3.73