It's leaking oil out of the back side of the turbo through the exhaust? Sure it's not the oil return tube that's leaking? That's the usual oil leak at the turbo, at least the one that you can normally see. If it is leaking out the exhaust side of the turbo you probably need to find a good shop to rebuild it or find a bearing cartridge that fits and do it yourself.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k