Thanks. As an engineer by trade, I'm all about the science side of things
I did a bit of reading in the article, and, if estimating 600 hp at the crank if the exhaust were to be fully unrestricted, I would need minimum dual 2.7" diameter piping to not create any backpressure:
2.2 cfm per open-pipe hp: 600 * 2.2 = 1320 cfm
115 cfm per square inch of piping for zero loss from backpressure: 1320 / 115 = 11.48 sq.in. total
Per exhaust bank: (11.48 sq.in. / 2 banks) = 5.74 sq.in per bank
5.74 sq.in. = 3.14159 * radius^2; radius = 1.35 in.
Therefore, ideal diameter = 2.7"
With a portion of mine at 2.5", the piping is slightly restrictive, and limits the system 'no backpressure' CFM per bank to: 115 cfm/sq.in. * 3.14159*(2.5" dia./2)^2 = 565 cfm.
[Obviously, this doesn't take into account my high flow cats, but I'm pretty sure that I've blown out the cores on them anyway...]
As such, mufflers flowing over 565 cfm would be effectively invisible in terms of creating significant back pressure. At least that gives me a baseline for what I should be looking into. It would be nice to know what the stock mufflers flow to know whether or not there's much restriction to them. I doubt that anyone has bench tested them, though.
As for the dynomax VTs, they sound great in theory, but the reviews that I've read noted a number of valve failures resulting in rattles.
2009 PBM G8 GT
TVS 1900 Maggie w/2.8" pulley (9-10 PSI), Maximizer LTs, High Flow Cats, LS9 injectors, Rotofab CAI, LC-2 WB, 40A KB BAP, TR6ix plugs, self tuned [250+ flashes], Camaro Paddle Shifters, UPR catch can, 4300k HIDs, Remote Start Heated Seat Control Module
, Aeroforce Interceptor Gauge, JBL GTO628's, JL 8w3v3's w/JBL P180.2, Bridgestone RE-11 tires