E.G.R valve is used to introduce exhaust gases into the intake air stream, its temp. controlled and submersed in fluid which makes it awkward and expensive. comes up as fault code P1405 (actual value voltage high/low or open circuit) and this is sending the incorrect rmp signal.
i looked into trying to lube it up
(behave) which can in some cases repair it apparently but knowing my luck its buggered.
theres too many friggin' valves and sensors too go wrong on this car