hello just joined and i think this site is fantastic i am getting a high pitched noise when i start the engine and it takes about 2 to 5 mins before it cuts out it doesnt sound normal has anyone had the same problem or might know what the problem might be thanx 
As iggy21uk said, what year, and which engine – presumably a V6 from your username…?
The Omegas have a secondary air pump which pumps air into the intake manifold when the engine is cold in order to reduce emissions. It is possible that this what you hear, though the typical notice it makes would be more like hammering and not a high pitch one – best way to check it is to either disconnect it or remove the relay or fuse controlling it. If the noise goes away then this is your problem.
If it is the secondary air pump, you will need to establish if it actually faulty – some noise is normal, but excessive noise means there is a problem with it. If the pump is proven to be faulty, it can generally not be repaired, you will need to either replace it (with a new unit or one from the scrap yard) or just disconnect it and live without it – it is not that important, and if you disconnect the pump the car will not fail the MOT because MOT testing is carried-out with the engine warmed-up to working temperature and by that time the pump would not have been working anyway.