I ran my old turbocharged engine with improperly spec'ed piston-to-wall clearance (.007" vs. .001"). This caused a TON of blowby in the cylinders, which blew a lot of oil into the cylinders. I found a lot of oil in my intake tubing and called up a turbocharger rebuild shop in Austin about getting a rebuild thinking that the seals in my Turbo had gone. It would have been the second Turbonetics turbo to do so, so I'd assumed the worst.
The company informed me that the "seal" in the turbo is really just two metal rings and that if I had excessive blowby, it would find its way over. I was apt to believe them as it saved me a $700 rebuild and rebalance.