Reading problems. Suggestions?

I have a V15 with an H20 modchip. All games boot up fine, but I've been noticing a few problems that have been coming up. In Initial D: Special Stage (Backup disc) the game freezes once it starts playing any kind of music. In IIDX 9th Style (Original disc) load times from one area to the next are ok at first, but get longer the more I play it. What could be the problem here? Is it due to the laser probably or the modchip? I've just read a little bit about cog and pot adjustments and am wondering if I should try those, but I'd like to hear others' opinions first.