yeh usually either oil coming out exhaust or through intercooler piping can meen seals are goin....but another common sign is the turbo changing noises.....
can make more spooling noises or grinding noise....its generally uncomon....but if you suspect any problems get a torch and look down the intake of the turbo...and move the blades around and make sure they arnt rubbing against the side of the compressor housing...do this WHEN THE CAR IS COLD....as ive seen too many people get burnt hands from doin it after boosting...lol