Is the best (reasonable)mod for the stock 454mag EFI to add an IMCO proflow exhaust,K+Nfilter and MSD ignition? I'm told this will net approx 4-6 mph 50-60hp. Is it necessary to reprogram the stock ECU? Any pitfalls? I'm told the Imco exhaust was designed for this engine specifically, netting the biggest results?!?Any info thanks...