An exhaust shop just isn't going to have the tools to clean those welds on the inside up. If you ask them they'll look at you like your nuts or something. If you want it done then you'll have to do it yourself. Just be careful about taking to much of the weld off with a dremel. If its welded inside and outside then taking off the inside won't hurt a thing. But if its inside welded only, then you'll have to be careful not to remove to much weld or you'll weaken the joint. I can't see those guys just welding only the inside so you shouldn't have any problems cleaning it up your self. Just do it.
Regards,
Dave
