I think this is a common problem, IIRC if it won't rev past 4000RPM but think I may be thinking of the petrols but obviously it's more prone to "Gumming up" on Dervs. Yes you are supposted to clean with cleaner whilst being very careful as the wires are delicate.

Do the Diesels not use a MAP sensor as there FI, I certainly know one of the varients does either the DI or the CI?

To answer your question yes, as the ECU will be missing one of it's inputs and so won't be able to make correct calculations, I would of thought this would bring the EML on as well?

Martin