Yes as most member says check the roof for differences between EVO8 and EVO8 MR. What is so different? Well the EVO8 MR has 2 thin bumps near the sides of the roof top (left and right side). These two lil bumps cannot be replicated unlike changing of rims, suspension, adding vortex generator.
The speedometer in EVO8 will say "Evolution" and the EVO8MR will say "Lancer"...
The headlights and taillights in EVO8MR will have smoked black instead of chrome reflector type in EVO8.
As mentioned, all those cosmetics can be changed, i know members who drive EVO8MR but having stock evo8 enkei rims, no vortex, stock evo8 lights, but the rooftop has the 2 thin bumps near the door pillar sides. It is very obvious between those two rooftops. The dealers will earn extra bucks by swapping those items for top up cash.
Price difference between both cars recond, i'd say EVO8'03yr around 150k, EVO8MR'04yr around 170k (i may be outdated tho..) If in doubt, take a picture of the rooftops and post in here, I'm sure many ppl can tell you whether if it's MR or not.