hi bought a 2005 a4 2.0 tdi 140 every now and then goes into limp mode, switch off engine restart everything fine took egr valve off cleaned it , it was not that bad really maf looks new, car a had turbo about a year ago guessing who ever did it cleaned egr then, while in limp mode got a code checked it was turbo underboost po 299 no engine light on dash and when car was restarted no fault code so trying to find what to check next can anyone help me thanks it is blb engine 170,000 miles looked at all pipes cant see any leaks someone said try vacuum actuator on the inlet manifold but not sure if this engine has one if it does its not in same place as the guy who told me about it , he said its near the egr anyone help,
