Originally Posted by URBiN~HURMiT

It's my understanding that this is a common problem with low mount turbos. With the turbos mounted low - the oil return line from the turbo to the oil pan doesn't have enough downward angle to allow gravity to do it's thing - thusly, the oil backs up into the turbo and then produces that smoke as it exits the engine via the exhaust.
Turbos mounted higher than the oil pan return don't have this problem.