The facts on a GT build:
(Posted by Chico)

I get a lot of PM's regarding building a GT so I thought I'd post here my opinions,first off as most know the common weak link in GT's & GTP's is the trans. and do'nt be fooled that the HD version is a whole lot better,now on with what I've found the 3.8 n/a can be built to run mid 13's with the following formula 1-cam either zzp gt1 or gt2 with a 3200stall convertor or Intense s/1 n/a cam ,it would also take a bump in compression to 10.5-1 by milling the heads 30k also a mild port job will help,as far as intake I would suggest a 3" FWI Iknow a lot will say 4" but remember on a n/a you will need air velocity not volume,now come to exhaust you will need a minimum of PEM's and 3" dp and hi-flow cat or race pipe if you can,another product that has potential is the zzp powerlog& rearported mnfld of course you may want to go to headers and I'm not saying not to it's just they are to expensive for the gain,of course you will need tuned pcm and most companies will tune for your mods,now a lot of guys just want to hang with stock GTP's at high 14's so aside from the head work and the cam (go with rocker's) you need the same mods ,I would suggest before modding that all your maintenace issues are resolved and your trans. is serviced and in good working order.