I just watched the new Best Motoring vid which tested the MR with Vortex generator, and the standard EVO. According to the vid, the MR has 35% more downforce toward the rear at 112mph. The high-speed stability is improved, but top speed was 3mph slower than less powerful standard EVO. (more drag from the generator)

 

I don't know if I'll 100% agree that the Vortex Generator was the cause to why the MR has a slower top speed. Several factors can contribute to it.