I'm new here guys! i dont have a buick GN, but i joined this forum cause you guys are turbo junkies and know your stuff. I have a '70 camaro rs/z28 with a 406 pushing about 425hp with about 9:1 compression. I was thinking about twin turbos with the budget upside-down header installation or even a single turbo with proper plumbing. can anyone tell me what would be the ideal turbo and A/R ratio to make a 9 sec. car with a single turbo? Thanx guys