Thanks for the ideas guys, Sorry Paul forgot to mention that the Upstream Lambda is switching, so mixture must be somewhere near. I will put the pipe up its posterior later today and check the gases. Sorry Steve this engine is a MAP engine, unfortunately with the ACR4 it gives a load figure for the MAP (17.5-23% at idle)not a pressure that I can compare with with my gauge, unless 100% is meant to equate to 100 kPa that is. I was more concerned about the funny noise,perhaps it's using so much ISCV input to keep the engine idling, will check later today. Shaun