recently i did some mods on my car which are : JTSVP Underdrive pulley, and Billet TB,K&N cai, Stock manifolds with 3 inch exhaust , NO cats and A small(14 in) Kooks race muffler on each side, Roe CMR tune, new spark plugs, and i have a cooler t-stat in the box, ready to go in, i feel the car accelerates quicker, and blows the tires quick too, but yesterday i got passed by a 2013 bmw M5!!!, which makes me wonder if i maybe losing too much back pressure. any ideas? P.S. I was in a mouintain ride and PPl were telling me they could see 3 foot long fireballs coming out of the exhaust of my car when i let of or got on the gas!!! Fun but i think not good for the engine!