Why are you surprised that you got walked by an M6 LS1? Those cars are low 13 second performers from the factory. My brother's stock 99 Z28 made 299rwhp with only a
K&N drop-in.
Even when my '98 GT was headswapped with 4.10 gears I only had a 1st and 2nd gear advantage over his mildly modded Z28, and that was because I had him waaay outgeared (3.37 1st gear + 4.10 vs his T-56 1st gear and 3.42s.)
An LS1 F-Body will come correct if driven properly, and in most cases they'll run idiot proof mid 13 second timeslips with a semi-competent driver, shifting at redline, with good conditions.
A solid shot of nitrous will give you what it takes to at least hang, and hopefully out drive him, but don't expect miracles. A near stock '96-98 GT is a low 14 second car, still a full second shy of the LS1. If you spray a hundred shot in a vacuum you're looking at full 1 second improvement, but keep in mind with nitrous comes traction issues, etc. There's no such thing as a "clean" power upgrade, other variables are always introduced.
If you really want to represent, headswap the car AND spray it, but then you'll REALLY be dealing with traction issues (which were readily apparent through 1st gear with my headswap, 4.10s, and 17" street tires.) A good set of taller drag radials will help alleviate that issue, and guarantee his view of your tailights begins much sooner.
Good luck, but remember not to underestimate the LS1, they're not easily dispatched. If you can race him from a dig, thats where you'll have your best shot. On the highway, with a 3rd gear downshift into his peak powerband, he's lethal.
. if that's the case a stock 97 GT with 100 shot will still fall behind on the highway if the SS has a decent pilot
shakes fist
