I have had good luck with my 84 190E as well.
The biggest headache for me has been the differential. But then again, my approach and execution was partly to blame. These units start to get noisy. Used ones are risky too.
On the gas motor the timing chain is another source of concern.
'84 190E 2.3
'83 Porsche 944 (track car)
'84 Porsche 944 (parts car)
85.5 Porsche 944 (sled)