I have run megaflow cats for a number of years with glasspak resonators, and magnaflow exhausts...truth be told as far as power...did not notice much of a difference until I added a K&N filter to the front end...then the difference was noticeable, but whether it was the combination or just the better flowing intake I do not know...I have four set ups but in 190E.s with this set up...one of them is on a 3.2 with a nominal 215 hp at the flywheel. I seem to get about 50,000 - 80,000 miles before replacement is needed.