1.8T AUQ Had a bad lamda sensor for a couple of months but when the car boosted and worked it was fine in the boost department. But now I have got the car back with a new thermostat and new lambda sensor it only gives me full boost up to around 4k revs then feels like there is none at all. Sometimes it gives me boost all the way, very intermittent at the moment. Only had the car back a day..... Any ideas please. Thanks,
