If the idle speed is still 3000rpm with the idle valve unplugged then there is physically more air getting into the engine than there should be. To me that rules out an electrical issue (loom or sensor) at this stage.

With the fitment of the swedish plenum, has the throttle cable tension changed? If you're happy there are no air leaks then that would be the first place i'd be looking.

As a side note, you will need to have the fuelling checked as the swedish plenum will move a lot more air at higher engine speeds, that will cause a lean mixture.