General problems? There's a few- and I've had/have nearly all of them. First- your engine mount is gonna want to fall out. If you aren't sure, take it to a dealer, have em run the VIN, and see if the recall has been done. Removing the VCTS and porting your intake mani is a LOT of fun- but will make the engine cranky eventually. The rods aren't the strongest things in the world, though they're not bad. The problem is too many people like to turn up the boost, and no ones got a decent line on fuel control yet. If you get a DP and have no control- you're going to see 20+psi spikes and sneeze your turbo seals. PTI sells a dope rebuild for the turbo once you do honk it, but it's expensive and you might as well go bigger. Really though, as long as you keep with the care and feeding, regular oil changes, keep an eye on your fuel trims and your PSI- you should be golden.
Also- the cosmic curse is a well known affliction in the ms3 community. We here know of two that have been totalled, one of which donated its driveline to a 2005- that promptly got hit. Several others nationally have been wrecked/started on fire/otherwise been bad luck. Hell, I just ORDERED one, and the engine mount bolt sheared off and tore apart the entire drive assembly on the drivers side of the car. New axle, new seals, the works. THAT was a fun time.