Hi Adam.
There's no EML in 1990 535i's -- it was used on later ('92) models, so that would explain why the EML light on the dash isn't going off (in my case, we pulled the bulb because it was ALWAYS staying on -- perhaps due to a short in the dash module -- and drained the battery).
My guess is that the car has some other problem -- perhaps related to the fuel delivery system (clogged/done fuel filter or a bad fuel pump/regulator). Have you done a stomp test?
best, whit