I posted the other day about finding a brand new set of Thorley tri-y's for a hundred bucks. After checking the part numbers and reading the posts I bought them. I did a search here on exhaust diameter and there seems to be a debate on crossover or not, and 2 1/4 or 2 1/2 inch in relation to torque and back pressure. This is for my driver and I will running duals, but still want to squeeze every bit of torque out I can. Any help will be greatly appreciated.