[teambowen]

I had a similar problem with my Mk4 gttdi golf.
It would go into limp mod once every morning.

I found i could turn the car off whilst moving which sounds very danderious, turn it back on and it would be fine for the rest of my journey.

I to went to vw and had the computer plugged in.
It came up with a high pressure warning but no fault.

I eventually found it was the boost charge sensor that plugs into the top of the intercooler, at least on mine anyway.
The sensor is directly under the windscream waster bottle and i think my problem was when i filled up the bottle, the spillage was going directly onto the switch/sensor.

I changed the sensor which was abt £45 and always take care filling the washer bottle up know and since then i have had no problems.

The position of the sensor can vary on different age cars but it will the either on the intercooler or in the pipework to the turbo.
Much the same as the air mass sensor is on the air inlet.

I hope this helps.

Jamie.