Hi Kim, The S type 2.7 Diesel has two EGR valves which can sometimes get sticky and won't open. They are at either side of the V6 and are a bit tricky to get at. To clear them out a good blast with the s button pressed sometimes works, but if it doesn't, get a can of Wynns EGR cleaner and follow the instructions which basically is to run the engine when at its normal operating temperature, take out the air filter on the right hand side of the engine at the front and spray down the air intake with revs at about 1200rmp. Use the whole can. You will need another person to keep the rpm steady at 1200 rpm and not exceeding 1500 rpm. I keep a can in the boot! They only cost about £9.50 and Halfords stock them. Regards, Peter.