1.8T turbo issues after smoking

[ginge]

Hi all,

I had a small issue before xmas where my footwell filled with water, and the resulting corrosion of cables caused the car to bilge white smoke (amongst ccm related other things)
I rewired the corroded cables, and unblocked the drains (thanks all that helped) and all was good.

After a couple of weeks of not driving the car I went out on the motorway, and I noticed the turbo doesn't seem to be playing nice.

I can hear the turbo whine at about 5000 revs, but the power produced is not noticeable. It used to kick in at about 2500 revs, and nearly snap my neck off.

I have checked the rewiring that I did (http://www.headfuzz.co.uk/vw_ccm) and it all seems good.

VAG-COM is showing no stored codes and comes back clean.

What can I do to test the turbo? Reading through the millions of pages of issues people have reported, I figure it could be the MAF, but my symptoms don't seem to match up, as I still have plenty of power (without turbo). Also I don't know where the MAF is.
You should assume I know nothing about engines, and looking under the bonnet of this thing scares me.

Help!

[ginge]

Anybody? Please help!