I would be grateful if anyone could help me get my head around the following - thanks:

The vehicle has a rough idle from cold (on rare occasions it misfires very badly). It improves greatly as the engine warms up and the cars performance is spot on either with normal driving or under load.

There are no fault codes.

When warmed-up the emissions are as follows:
CO: 0.00%, CO2: 14.7%, HC: 1ppm, O2: 0.82%, Lambda: 1.04

Fuel trims are as follows: Additive = 0.9 - 1.0% & multiplicative = 0% (even after lots of running). Readings are the same whether from VAG-COM or Bosch.

There are no intake or exhaust leaks (Smoke Pro tested) (confirming the additive fuel trim reading).

The exhaust back pressure is not excessive at idle or under load (tested using guage screwed into pre-cat oxygen sensor socket).

I have scoped the AMM and it follows the TPS opening pattern nicely with a peak response of 4.6V (which confirms that we might expect the multiplicative fuel trim to be close to zero).

The lambda sensor (broadband) does not read excessively rich or lean (lambda % reading) and testing of the heater circuit gives 3ohms when disconnected and cold, and a nicely square switched voltage (0 - B+ VOlts) is observed.

The throttle body is spotless and has been adapted with no change in the symptoms.

The over-run cut-off valve and crankcase breather pressure control valve were both replaced last year.

Any thoughts on what should be my next step would be greatly appreciated!

Thanks, Barney.