Zetec s limp mode

[Tom0]

Hi guys recently I’ve had a problem with my Ford fiesta zetec s it is essentially going into limp mode when I accelerate from 40-60 mph if I put my foot down enough as well as that the car was overheating. I took it to Ford and they did diag checks and saw it was overboost but never really came back to it. They ran all the tests and it came back as overheating but all the other tests they did such as block tests etc etc said it was all fine but what they did find was the thermostats weren’t opening and new water pumps were needed as well as a fan. So at that stage I got two new water pumps fitted and thermostats fitted wasn’t cheap lol. Two days after taking the car in it went into limp mode again so I took it back to Ford and they re did there’s tests checked everything over three times and they said Ford were recommending a new engine or to have a look at the head gasket. So took it to nev’ll fix it and they said it could be the turbo and again after doing all the tests nothing out of place apart from a turbo pipe with a hole in it so have had that replaced car temperature wise seems better now but again two days after putting my foot down a little bit it goes into limp mode any ideas on what it could be? 
thanks Tom

[DaveT70]

Has it stopped over heating?

Check the one way valve in the turbo vac feed hose from the pump to the solenoid

[Tom0]

Yeah it’s still mildly hot coming through the air vents in the car but yeah I would say so and ok cheers I’ll have a look