Seen a few posts along the same lines of this but can't find a solution, wen driving at 69mph it's fine, soon as I get 70mph and 2000rpm it limps out, then key off an on it resets, there is underboost fau!t showing. Had dpf problems but changed glow plugs,intercooler and thermostat that's all sorted, just this underboost and limp mode, local garage says acuator needs sevice but few posts on here pointing towards egr valve, I'm a plasterer so 'I know nothing' (in a Manuel voice)
Thanks in advance.
2016 transit 350 2.2
125k miles