Noticed a strange issue with my Focus last week, a loss of power. Couldn’t work out why where or how. It had only been a short drive so parked up. When I came back to car, drove fine with normal power.

Yesterday we drove down to Exeter. On the way, about half way into the drive, I lost power again. Basically felt like the turbo had dropped out, no power up hills, no overboost (or whatever it’s called). I drove on managigg Bt the situation. Stopped in a lay-by, turned off the car for a few mins, back on, all fine, turbo whirring up and giving power as normal. I kept driving, got into 6th for a bit on the motorway then the power dropped again.

i theorised it was 6th gear that seems to be dropping it out. Today, I drove as normal, power as expected. Dropped it into 6th and shortly after power dropped out. Stopped. Turned off car, waited a couple of mins then started again. For the rest of the journey, I didn’t use 6th and the power remained as expected and turbo kicked in as usual. 
 

I see a lot of posts on this being a split pipe, blown turbo, vacuum pump etc. The thing is, the car works fine, no additional noises, no smoke, leaks that I can see other than the drop out of power. The only trigger I can replicate is 6th gear which suggests something is shutting off the turbo at this point for a reason unknown, only to be reset by the ignition going off. 
 

Ill get it into dealer, but wondered if anyone had experienced something as weird as this and if so, what the remedy was.

It all seems to point to either cracked pipes or brake issues but as your not esperiencing any brake issues check all your pipes for splits.