1990 BMW 325 fuel injection system

At that mileage, have you considered replacement of the fuel pump? I would. ♥

Greetings,
Thanks for taking time out to reply.

Yes I have considered it. As the one in the car now is howling. Yet, I wonder, if the injectors may need to be replaced too.

The pump started getting louder when I used some fuels that had invigorate in them (alcohol). The dealership said to use Shell, in our area and forcefully said do not use the fuel with invigorate in it, nor the local mom and pop fuels. My brother has a x5, and when he first got his truck the dealer let the fuel get too low. When we somehow got it to the gas station, fueled it, it began to make howling sounds and ran badly. He too switched fuels, and this is what made me ask is it the injectors as they sometimes act funny if contanimates get past the checs and balances and make it to them.

Cleaning, rather then replacement(they're expensive those injectors!) would be something I would try before replacing six injectors. Have you tried removal of the fuel rail and inspection of the spray patterns? There is also a possibility of crud built up in the intake plenum and perhaps around the injectors themselves. And replace that fuel pump so it does not strand you somewhere waiting for the tow truck. ♥