When you installed these did the cats get removed from the OEM system? If I understand correctly the cats are in the mid-pipe and the Delkevics come with a mid-pipe replacement correct? Have you noticed any difference in performance or MPG results? As far as MPG I checked the last time I road by filling up before I left, and then filling up on my way back home. I only rode like 86 miles but what I found was startling to me. My dash computer displayed something like 46mpg but my calculator showed that my actual was 55mpg. I was very pleased to know that the actual was much better than the computer display. I also believe the gas gauge is way off and shows much less fuel than is actually in the tank. I DON'T KNOW IF ALL THAT IS IN THE TANK IS TOTALLY USABLE and don't want to test this but quite often my gauge shows empty and I can't get more than 4.5 gals or so in the bike. I believe it is supposed to hold 6.0 gals.