I recently got my 400EX motor rebuilt. We replaced all of the gaskets except for two exhaust seals. I have a Curtis Sparks Racing X4 full exhaust system. When we took the exhaust off to send the engine out we did not notice any seals in the exhaust ports. So when we went to put it back together we did not put the seals in. Do the seals only go on with the stock exhaust? Do some aftermarket exhausts mount without using seals? Any help would be appreciated.

-Thanks