BMW Repair: 1985 535i dies sometimes, old american cars, sensor side

Question
Hi Don, thank you in advance for your time.  I usually work on old american cars w/o computers and this is my first BMW, so I do not know what everything is under the hood.  I have an '85 535i with 260,000 miles and it usually runs great, however it occasionally dies under load or not and is hard to start for awhile afterward.  When it does start, I cannot keep the rpm up at first then eventually it runs fine again,only to do it again the next day or the day after that.  About 1,500 miles ago, I changed the oil and plugs and it ran great for quite some time.  This morning I changed the fuel filter, rotor and cap.  After about 20min./15miles it did it again.  Any advice you could give me would be greatly appreciated.

Thanks a ton, Dan

Answer
I'm glad you have come to driving a BMW.Your problem comes with a question do you have spark when it dies?If not I would look at the reference sensor they intermittently stop working.You can measure the resistance between the terminals on the sensor side I beleive it is around 96 ohms.The grey terminal..located on the trans