[reggit]

It sounds induction(ish), check for split pipes (the one on the turbo is popular), or blown intercooler. These could give you an oil leak, but I wouldn't say major. It would also cause it to smoke on throttle (not sure off throttle).
Also check around the bellhousing, there's an oil core plug under there that can fail and cause a major oil leak, which can spit oil onto the exhaust and cause an oil haze.