I am going with the TTI 2.5" w/X pipe but using Dynomax Ultraflow muffs instead of the Super Turbos that come with the kit, but I'll also be using exhaust manifolds instead of headers on my 440-6...x pipe supposed to be a little more quiet than h pipe, ultraflows will flow a little more than the turbos...fwiw, I loved how my cuda sounded with the Hooker Super Comp headers straight through to the 3 chamber Flowmasters I had on for years...