Engine management stays on

have you modified your air filter

Found site looking for a solution to a similar problem and wondered if anyone could help.

2006 1.6 tdi focus c-max

Basically car was in for service just over a week ago, the following day the systems fault and red light came on. This appears to be coming on when accelerating on an incline, and mostly when car gets to 55mph. Once light and message show the power seems to die and lose acceleration up hill and stays like this until I turn engine off and on again.

Acceleration on flat is fine and car is running great as normal, even drives at 80 on motorway including accelerating so long as I don't accelerate going up hill.

Had back into garage and they couldn't get code, so took back in with light and message displaying and a turbo fault code was registered.

Garage has checked the turbo, egr valve, all hoses etc and everything seems to be fine. Suggested going to Ford garage and ask them to check programming.

Air filter was replaced in service, hence me replying to previous post asking if air filter was changed.

Thanks in advance for any ideas.