[urq] Clutch or wastegate or what?

[SpotatAshleys]

Just when I thought it was all over, the car finished, on the road, problems overcome and running in, I'm hitting problems.
If you have any thoughts, they'd be very welcome. Here's the symptoms:

Pull away in first, car pulls strongly up to 4000. (I'm sticking to 4000 max whilst running in the new motor). It pulls strongly in second up to 4000. You can hear the turbo spool up as boost builds. Boost approaches 1 bar before the change up as far as I can see. It's difficult to watch revs, boost gauge and road. 
In third it pulls fairly well up to about 3 and then whistles and the power drops off but revs appear to rise.
The same in fourth and fifth. Once it gets some boost in these gears it just whistles, the power goes but the revs appear to rise.

Heres the details:
New engine (WR) largely stock.
Wastegate has been apart and is not yet set right. (How deep in from the top face should the adjustment screw be for 1 bar boost?)
The Wastegate spring is I believe a Dialynx 1 bar 
The ECU is sealed with a Dialynx sticker and I believe it may have had the diode mod.
The clutch is brand new, 300 miles old now.
There are no fluids coming out of the bottom of the bell housing indicating fluid contamination of the clutch plate.
No oil loss from engine.

Could it be a slipping clutch? - I think it is but can't think why it should be.
Is it the wastegate simply dumping pressure because the spring is not correctly set?
If the latter why does the rev counter rise?
I can't see that it can be the clutch but everything points to it.
If it is why is it OK in first and second?

I am at a loss to identify the real problem here. Any suggestions gratefully received.

Thanks and Happy New Year to you all.

Keith
87 WR