Many LS1's I have come across are stock. The ones that were modded, all had problems. They all would hit their rev limiters. I never noticed with my Cobra, because I was so far ahead of them, but I remeber being a teen, racing one, in my 92 5spd GT. I only had
Flowmaster weld in mufflers, and a
BBK CAI, and I took one 3 times because his H/C/I LS1 hit the rev limiter in 2nd and 3rd gears!! If I were you, I would buy a stock one.