Still having sudden power loss on my Fabia 5J MK2 105 BHP 1.9TDI, it does not happen every time and only seems to happen when in a high gear 4/5 and under boost on a rising hill,, the car losses power and goes like if in limp mode with no turbo boost but you can still drive it like a non turbo car. Stop the car re-start and away we go again no problem . No warning light or anything shows can then drive around for a week or month and nothing then all of a sudden it comes back again when going up a slight hill in 4th or 5th gear and the turbo is starting to boost, but as before not every time, in lower gears no issue with the turbo boost at all does it every time,

Cleaned the EGR valve pipes look good and tight on all fittings, changed fuel filter air filter and have even changed the oil again

Have had it checked out for faults nothing showing tried to take it to dealers when in limp mode but soon as they turn it off it's ok again when they plug it in and reset the system

Don't want to spend stupid money changing parts that are not broken but the dealers seem to want to do this suggesting stating with the turbo and then moving on to the pedal unit Erg unit and a unit they called a vac unit under the bonnet top of the wing right hand side by drivers door and then one of them suggested that I might need to replace the ECU unit so far we are into about £3500.00 and that's just parts Car has done 80,000 from new 2008 and always been serviced every year whatever mileage  

The usual cause of that kind of thing is a sticking VNT mechanism in the turbo, but that should log a fault code.

Sounds like a classic overboost fault

A-Ha problem is now sorted, the engine management came on the other day for the first time after it went into limp home mode so stooped turned car off restated back to normal but the light stayed on so took the car and had it plugged in,fault code insufficient turbo boost.

The top turbo hose that goes into the EGR unit was tight in the socket but the seal on the metal ring was worn and not sealing correctly but only failing at certain times and conditions, a new pipe and £92.00 from VW for a new one later and so far no issues with loss of power or engine light coming on