Yeah Jeff, same 87 300TD. Sorry for the confusion. The easiest way to describe the oil tube's location is hood-up to look down on the turbo between the 2 brass colored compression fittings. About 6" down You can see the top of the odd shaped flat plate with two 6mm allens 30mm apart. One of the allens is right between the brass colored connector joining the 2 exhaust manifolds. That odd shaped flat plate is the end of the oil tube. The tube is routed under the exhaust and into the engine block mid-engine with a 17mm bolt that presses the tube's flange into the block - like a gas compression fitting.

The gasket on the flat end was ripped, but not leaking. I removed it and applied some black RTV. I can also probably cut one to replace it. But it is the other end that is leaking.

The carbon build up was after the crossover tube joins the bracket - the unit to the front of the bracket - also held on with two 6mm allens - and it has a vacuum line running out forward. I found the carbon-build-up when I removed those two allens.