Yay! Another MK1 Cabby GTi (DX engine) cold start idle issue!

Yay, another idle problem for you to help with!

1991 MK1 GTi Cabriolet Rivage. Original engine, it's standard.

Cold start idle is very low. 600rpm, wanting to cut out and stall low. As it warms up it becomes progressively better until it sits around 950-1000 quite happily.
Idle fluctuates ever so slightly, maybe 25-50rpm maximum.
Idle speed is slightly intermittent, i.e. one journey it might be  950rpm, on the way back 1050rpm

The AAV seems to be working (squeeze the air pipe when cold and the engine chokes, when warm no change)
Timing is spot on, ignition and cambelt
New rotor arm, cap, HT's, plugs and coil.
The idle screw seems tight and it does adjust the idle, I've done CO2 by ear but I'm popping to my local garage to get onto their equipment. Should it read 1-2% on idle?

Any help appreciated.

 

aye about 1.8% is what i woudl like to see.

check everything over as per this thread, but ignore the 16v specific bits:
http://www.vwgolfmk2.co.uk/forum/viewtopic.php?f=37&t=25972

rubjonny said

aye about 1.8% is what i woudl like to see.

check everything over as per this thread, but ignore the 16v specific bits:
http://www.vwgolfmk2.co.uk/forum/viewtopic.php?f=37&t=25972

You the man. Thanks!