I don't know about running 4an line. I had 4an on my truck before and it did not work very well for me. I then switched to a 6an and ran a .125 jet in a single stage with no progressive controller and well lets just say that screamed but with that big of shot you can do some real motor damage.. Just make sure your boost and rpms are up before feeding too much N2o.
Good luck,
Jon
I know a guy around here that has a 03 or 04 gt with a blower pushing 14 psi and he's not too much of a challenge for my set up on #2 sold all the nitrous stuff couldn't have it on the truck for pulling so I got rid of it... don't know what my track time would be but he said he's in the mid to low twelves the few times he has went to the track... I can beat him from a dead stop"with boost", and roll ons anywhere from 10-80mphs. I know he has had custom tuning by a guy who really knows his gas motors with the fast systems, he builds motors for pro street draggesters, don't know if has heads on it, last i knew he didn't..