I have been doing some research on this site but am still unsure what to do. I have a 08 wr450f supermoto with an ASI kit, box lid removed, and the pee shooter removed from the exhaust can. I was looking at upgrading my exhaust but just wanted to go with a mega bomb header for now. But it appears most people say the header is useless with the stock can. Are these people refering to the can with the restriction in. And I've also noticed some people said they seen a bigger increase with just the factory 4.1 slip on with stock header as apposed to the mega bomb with the stock can. Some good input would be appriciated so I can get my mind made up lol.