B5.5 TDI130 sport PD engine Rough running and no power!

[alex.mc]

Hi All,
I have asked this question eslewhere, but think a UK forum is probably a better bet.

I have an 02 B5.5 TDI130 S with the PD engine. It has always been a great car. Powerful enough, smooth, roomy, economical, starts on the button even in deep freeze etc........

I came back from a an hour and half's drive and in the last 20 miles it felt like I was losing power. I was trundling along so it wasn't noticeable really. Came to a long hill, and it was very slow indeed. No power. I noticed it felt quite normal at small throttle openings and gentle accelerations.
Got home and the car was perfect in starting, and idling, and totally normal if gently revved to no more than 1800 rpm. Above this or aggresive throttle produced a rough running akin to running on 3 cyls, along with light coloured smoke if held.

A chap read some fault codes for me, and suggested the coolant temp sensor was buggered. I have changed the CTS and it's still the same. The sensor was indeed buggered as I had noticed a day or so before the gauge on the dash was reading zero. I'd ignored it as I'd confirmed that the engine was okay for coolant and not overheating. The gauge has begun reading correctly since.

It has been suggested that the pipes to the intercooler may be split. I have visually checked the one under the airbox/turbo, and although oily it seems okay. I can't honestly get anyone I know to try and gently rev the engine correctly though to feel if any boost is occurring in the rubber pipework though. What help I got was not great, but I get the impression there's not much boost happening.

So my questions are:
Do the turbos give up completely at all? How can I check this.
The engine is a bit on the oily side, despite how well it used to run. Would a gungey MAF cause this kind of problem?
Would a complete loss of boost(from a split I haven't yet found, or split intercooler etc) cause these symptoms? The rough running etc...... yet perfect starting and idling and low revs behaviour?

Possibly a coincidence.... I noticed yesterday that when revved up mand running rough, like a misfire...... the ESP like would flicker on kind of in tune with the misfiring??? Any relevance?

Could really do with some pointers here, suggestions where to focus etc....

Many thanks in advance.