Yep, found it. It's definitely wet. But it looks like it's a sealed unit so no way of drying it out without cutting it open. I might give that a try and then tape it up until I can get an new one. I've just run the car round the block with the filter removed. The engine light stayed off but...

Thanks for the help guys, I'll check those items. I guess the next question will be, if it is the turbo boost solenoid filter, how do I prevent this happening again ?

Hi All My '05 Sport TDi is losing power after it's had a soaking, typically soon after splashing through standing water. The engine management light comes on and it goes into a sort of limp-home mode - power is down and the revs appear to be limited to approx 2500. It clears once it's dried...