hi all hope somebody can be of help here

i have recently had my cambelt done and only owned the car 3weeks and its a very clean and smart example of a 54plate st170

it has circa 80k on the clock with full history

the engine light came on whilst driving through traffic at around 3-4k rpm the other day so i checked the code with my ebay code reader and found oddly that it wa the manifold stuck open code....but the imrc is working as it should with no odd noises other than when the ignition is turned to pos2 you can hear it buzzing over to the correct position but makes no odd ticking or clonking noises from the imrc box on the bulkhead

the 5k engine note changes although personally i dont feel any really difference to any other car in power change at those revs.... but it definately feels about right after coming from a bmw 325 and 328i ,....

the level is pulling the manifold clip towards the radiator side of the engine bay when started....so im assuming it is releasing the cable when over 5k ish revs and the manifold spring moves the flaps back to home position until below 5k again

does anybody know if i could change the manifold return spring with any great ease...with the manifold on the car seeing as sometime when pulling the manifold control wheel (where clip mounts) if i pull quite hard the manifold seems to occasionally stick into one or the other positon as if the return spring for the manifold is not quite man enough.....

anyway after messing about finding nothing odd isnide the imrc box i simply sprayed it with wd40 when i took it off the other day and sprayed some 20ml or so of wd40 down into the inelt flap via the intake rubber pipe and since doing this i havent had any engine light whatsoever for the 30mile mixed driving i have done since.....

if there anyway of stopping the manifold from getting stuck open ....it literally only takes a light tap with my hand on the manifold top to make it spring back into place....i am assuming this is what sends the light on because the cable doesnt return properly in the set amount of time inside the imrc ????