Maybe u have a strong runner or just ran into a bad ls1. I know with my new mods i will either be pulling this cobra or it will be even.sounds like you beat the driver. ive ran similiar LS1's, and it was no where near that close, and i dont even have a pulley. just full exhaust, and intake.
the one that stayed right beside me though had longtubes, heavy cam, not sure about heads, intake, and a tune. i couldnt shake him off for the life of me.
I had a short run with cobra before the pulley and tune. So he just had full exhaust and intake. The run was cut short because of traffic in my lane. It was from about 70 and we went for about a gear and a half. Maybe til 110-115. I jumped out about a car and he pulled to about my mirror and i had to let off with me a little ahead. I know it wasn't a long run but i still held him off