This is one of the dumbest things Ive ever heard. Because obviously your not to informed/educated/mechanically inclined ect...a general rule of thumb with ANY combustion engine...MORE AIR(in and or out)+MORE GAS=MORE POWER (including torque) without any type of pretext, it is literally impossible to say that he would gain or lose power. Adding exhaust, coupled with making sure the fuel ratio and intake is sufficient will always increase power, always. Every time I hear somebody say back pressure in combination with any type of HP advice, i have to giggle a bit. I THINK what your talking about, or the only LOGICAL thing you may be referring to, is the "scavenging" of exhaust gas which can LITERALLY be affected by a dent in the pipe, whether increased or decreased. Increased flow(intake and exhaust) with self tuning EFI, WILL ALWAYS increase power. I never understood how somebody gets the idea in their head that choking (back-pressure i believe you say) a motor, Will increase torque. 🤣🤣🤣