I have the 4meg Ram cart import thingy AND X-Men Vs. Street Fighter... works like a charm. I have like 10 Japanese games for my Saturn and they all work perfectly with it. the ONLY thing that didn't work was my US Version of Panzer Dragoon Saga, but that was because Sega did it to prevent people from cheating LOL
But yeah, what game did you try and have not work?