thats why i said "a stretch" i was just estimating, i only see bout 12hp and 8tq gain with I/H/E. i've heard of more but never actually seen the numbers.

 

backpressure is bad no matter what. a properly designed system, does not need backpressure inducing items to tune the exhaust flow to suit the motor

 

thats not always true, i know some cars can run efficiently with very little backpressure, but with the xA/B some degree can give better results because scavenging between pulses isn't very high with the factory diameter on the exhaust. and even with corroborators being a thing of the past, smaller engines need the pressure to help produce more Hp and Tq by holding back the exhaust, it helps them to build rpm.

i don't mean to stand you up Malibuguy (i'm sure you are way more experienced in this subject than i am) but i know back pressure isn't ALWAYS bad, and to add to that you mentioned "properly designed system" which i assume the xA/B is, but its not exactly as efficient as a Mercedes might be.