The manifold bolts as well as all of the turbo housing bolts and dump pipe bolts are prone to come loose, this should be done every service. The other thing is the turbo oil screen, do a search on it, but you can either replace it, or remove it all together if it hasnt already been done. I chucked mine out and havent had any issues... Otherwise, just keep the TB clean, give the boost solenoid a hit of WD40 every so often and make sure the piping is always tight. If you have just bought it, I would take it for a quick dyno run, just to make sure everything is ship shape and nothing dodgy has been done....