The Nicasil was attacked by high sulphur levels in the US gasoline. Grade of gas used made no difference. There were problems in Europe too but they did not draw as much notice.
But if it is good now it will stay good because all of the US gasoline now seems to be low enough in sulphur to avoid damage.
Have whoever is doing your tune-up tell you about the condition of the back two sparkplugs on the passenger side of the engine.
If they are the same color as the rest of the plugs you have a good engine. If they are really dark or oil fouled you probably don't have a good engine.
BMW was quite cagey about the service action. It was not broadly announced to the owners and the original replacement blocks were Nicasil lined too. Later replacements blocks were Alusil.
The running test that BMW service writers used (but only if YOU complained about rough idle) was to open the drivers door with the car idling. If it was wagging up and down at the outer end they would start the process of testing and part replacement. That would continue on to block replacement if deemed necessary.
The Warranty was extended to 6 years from in service date or 100,000 miles which ever came first. So ALL E31s, E32s and the 1995 E38 are all beyond the extended warranty period. BMW will not bend at the moment
The PCV valve on the back of the intake manifold and all of the original intake manifold seals tend to dry up and also cause the same symptoms.
I had a '94 740 that was BAD
If you put Mobile 1 15/50 in it and changed often it only smoked a little on startup and at full throttle. But would foul the back plug in about a month. With conventional oil it was a mosquito fogger on start up.
My '95 840 is also a Nicasil V8. At 144,000 miles I pulled the spark plugs that had been in for the 20,000 miles that I had owned the car and they were all uniform in color with no signs of oil
The difference was where the cars were operated in their early years. The 740 came from the midwest and the 840 was a California car.
Now that I feel that I have spread enough depression for the Holiday I suppose that I can quit typing.
Good luck and hope yours is OK
BTW the next Sedan I buy will probably be another E32 740.