92' 518i Fuel starvation on no 1 cyl.

[scotia900]

Hi all,
New to forum, need a little help, got a 1992 e34 518i, it seems to have a fuel starvation problem, it ticks over okay, when you accelerate it struggles between 1500 and 3000 rpms sometimes it clears and runs fine other days it feels like you are running on 3, i've changed plugs, leads distributor, filter, crank pick up sensor etc, i noticed when i took the intake manifold off after running it, that 2,3,4 cyl had oil/fuel film in the ports but no 1 was bone dry? the plugs however look all the same, any idea's? i also swapped injectors 1,2 around but made no difference, is it possible for the ecu to break down just 1 injector? it doesn't back fire or really splutter,