Car is 1987 740T with B230 engine and AT.
The other day I drove it with A/C on. After approx. 20 min
it shut off when I had to use the brake. Restarted fine, but each time
I took my foot off the accel. the RPMs would drop, and it would
have hard time running. Turned A/C off, and made it home.
While watching the RPM gauge, I noticed occasional sudden drop,
and again, few time engine shut off entirely. It does restart fine each
and every time, but it has hard timer running with consistent RPMs.
It may go for a min or two, before another RMP drop.
Any ideas ? Throttle body has been cleaned a month ago. It has new plugs.
Vacuum hoses too have been replaced, as well as the turbo hoses.
When the car idles, it does so at approx. 800 RPM.

We've had a lot of trouble with intake hoses on our 87 760T.

At 50K it needed a new intake hose from the amm to the compressor, but we didn't figure it out for 20-30K...just sucked up the poor bottom end response (the turbo covered it up when it started sucking...it was running somewhat lean). Had to replace the same 180$-prob 220 now hose last year at around 240K. It doesn't like the turbo heat and the oil from the turbo bearings (comes around the compressor bypass valve.).

Also make sure the hoses from the intercooler to the intake tubing are good. And the hose from the intake tubing to the aic motor goes bad.

Frankly, if they've never been replaced, I'd replace them all if I had a used 87 today....