Hello everyone, I have 190K mi 1988 745Ti, M46, with turbo plus package from the factory.

My issue is that I hear some hissing / sucking noise when I full throttle, which is more prominent over 4000rpm. People in the back seat tells me that it's quite loud for them to hear the sound.

I thought that this issue could be the split hose from the in-tank fuel pump to the sender assembly's metal line, so I replaced that one with 5/16th size hose. No difference what so ever after replacing the hose- so I thought I have placed the pump sock in a wrong angle. I pulled the fuel sender assembly again- and changed the sock angle. It's still making the air sucking noise.

Even with the air sucking sound, the car gives very good power on stable boost upon WOT, no cutting out what so ever. Fuel pumps' noise is on a normal level. I replaced the Fuel pressure regulator before the fuel rail and the fuel filter- which was filthy.(it puked out black gasoline for a long time from the input side)

I just want to solve this problem, since I am worrying if this noise is sign of something that's gonna make the fuel pump die.

Any thoughts would be greatly appreciated!

Thanks,

Alex.K