Even modded they aren't that interesting. A local guy has one with a FMIC and exhaust. Still horribly slow. He lost to an all-motor Civic not too long ago. Supposedly the block can't hold much more than 12 psi safely.
Yeah you think the MSP is slow, my dad has an MP3, basically unturboed MSP. Slower than shit, but let me tell you, it handles over 100x better than the WRX. Next summer I am hoping to put on a header and catback exhaust along w/ some sort of intake to get the car a little more giddy up. But damn that car is ungodly slow.