Exhaust leaks leave a sooty mess that needs to be scrubbed off. Recent engine oil residue usually comes clean with a spritz of brake parts cleaner.

If it's on the block below the exhaust manifold gasket, it might be leaking valve stem seals. How does it look around the turbo oil supply fitting on the block? How does it look where the drain pipe attaches to the turbo? How's the area around the chain tensioner? Is there a tensioner crush washer in the replaced parts list? Take a torque wrench to it to make sure it's tightened to spec.

How's the hood pad? I forgot to replace the oil filler cap once and it soaked a corner of the pad. Years later it still leaves oil on the rubber strip atop the air cleaner barrier.

Sixto
87 300D