Loss of power?? HELP

So I’m at a loss here, my 95 3litre turbo diesel baby has lost significant power, as though the turbo is intermittently working, I used to get power and turbo wind at 2500rpm now I can barely make it up steep inclines on the highway without dropping it back to 3rd gear (automatic btw!!) or using overdrive to make sure the revs sit above 3k. There is a hole in the exhaust manifold that bolts to the engine, it now sounds like I’m starting a f&$king lawnmower some mornings! That’s not all, out of this hole is obvious exhaust coming out but also a blackened sludge not as runny as oil, but more a thickened black sludge. I’m at a loss as to what could be happening here and would love to hear some advice on this or if there’s anyone who has ever had similar experiences??
Thank you in advance!!

Hardly surprising looseing power sounds like serious problems with exhaust and probably EGR inlet manifold gunged up turbo pressure sensor too ,if oil is rely bad probably worn pistons is it very high mileage if so its probably kneads a engine swap.

The sludge is relatively normal but I'd say it's worse because of bad running.
Your problem sounds 3-fold.
1: Fix the exhaust manifold.
2: Replace the Turbo Pressure sensor filter and clean the feed-tube to it.
3: Remove the intake manifold & clean it.

That power loss symptom usually relates directly to the Sensor and the filter. 1&2 are critical, 3 is a good idea.