Most dealers that I know won't. It will really depend on the technicians. No different from taking it to Jiffy lube when they look under their car.

Mitsu does have the ability to screw with your warrenty though.

 

You shouldnt have any problems with that at all. Most evo owners i know dont have cats on their cars and have never had any problems with anything like that.

 

+1 they dont care. Last time I went, the tech commented on how nice my exhaust was