i picked up hella topend with my headers. i did feel like i lost a tad of low end with out a cat (back pressure is good sometimes) but it loves it up top, specially toped with some rockers.
Better for the launch. I noticed a drop in low end tq. But mid and high end tq was well worth it I'm pretty sure my mazda would own my regal after header install, not so much before the headers.
2000 Buick Regal Gs. 14.811@93.61 mph Bald Tires, Custom CAI, Stock with Stock GP Dual Exhaust. 2000 Ford Taurus SeS "FFV", 2001 Ford CVPI "Police Interceptor" 1995 Mazda Mx-6 LS