Haven't it crossed your mind that's something wrong on your side? Everyone's reporting fullspeed on gambatte except you it seems. Well anyway I tried both games you said, Belmont's Revenge is running beautifully at 60fps, while V-Rally seems to be one of those crazy pseudo-3D racing games with tons of scrolling effects like Wacky Races, so I'm getting between 47 - 50fps on it.
Bottomline is everything that doesn't try crazy things like that will run fullspeed.
I'm using an OG 3DS of course, 9.2 with .cia. I think somebody's been using ninjhax around here and reported fullspeeds as well.