The S would be alot better over the A. I went through this last winter and after doing tons of searches and asking lots of people around me with blowers, I went with the S. The A is good, but most people that had one had it upgraded to and S anyway. It costs more over time to do it that way, plus the S trim gives you all the extras:T-Rex, bypass valve, boost retard. It rarely has problems, and can easily be made to run harder also with pulley swaps. I was ecstatic to find out how much power I made doing nothing to the car othere than the blower. Granted, I had intake, heads cam, etc, but all my parts are box stock bolt ons.
I strongly suggest setting money aside for: 36 lbs injectors or larger(Esp if getting heads/cam soon if not already) an 80 mm mass air (LaRocca says this size helps add a pound of boost or two), and a professional dyno tune. Trust me on this, I blew my head gaskets after a few weeks. It is good piece of mind and keeps breakage to a minimum.
Done with the Vortech advertisement, lol!
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See my car
HERE
93 GT Red/Grey
S trim, Edelbrock 6037 heads, E cam, BBK longtubes w/cats, 3 chamber Flowmasters, Cobra intake, Kirban fuel regulator, BBK 70mm t.b., 75mm Pro-M meter, 1.7 roller rockers, Mac upper and lower strut tower braces, FMS lowering springs, Factory Five upper and lower control arms, Speedware Cobra R 17X9 wheels, 3.73 gears & more.
DYNO=435.6 hp/405.1 tq at rear wheels.