the stock mini system splits into a dual at the rear. a straight shot out may be able to give a 13hp increase. though I dont know if changing the number of discs would make 5. i didnt look at the dynos, and its too late to research supertrapp technology, but it doesnt sound plausible
1.8,Miata FM ECU, custom intake, header, exhaust
Fred Uptagrafft's n/a 1.8 in a '90 car, with FM ECU, k&n behind headlight, RB header, supertrapp (LOUD!), stock boneyard motor, gasket matched. Very healthy! Stock 1.8 shown on chart for comparison.
I just don't like the look of the SuperTrap. I saw an Integra the other day with one, and seeing it in person didn't change my opinion on it. I don't see how the number of discs in a muffler can add horsepower either