For a 600-620ish HP (Flywheel) combo with just under a 600 lift cam and only being spun to 6300, how much if any ET lost would there be with using a 1 3/4" header vs 2"? Car is 3150lbs. TTI headers in a A-Body. TTI recommends their 1 3/4 for 300-475HP, and their 2" for 500-750HP, not sure if that's flywheel or rear wheel.