the stock pipe from the header collection to the canister is very large probably 3 inches?? the full exhaust i just purchased for my bike made by D&D has similar sized header pipes but when they collect the pipe stays smaller, 2 inches. just making sure thats how its supposed to be because it looks so much smaller than stock pipe. thanks guys!!!

 

The stock pipe is larger due to the restricted flow of the muffler. The D&D is a lot freer flowing and that is why it's smaller fo a little back pressure.

 

cool, exactly my prediction