Rough cold start

[tilly05]

1.8 20v t
Thermostat is broken/missing - not sure yet only jad the car 1 day
Anyway. Started car at 6am temp was -0.5deg, when revved upon returning to idle the eevs dropped right off, not enough to stall the car but enough to judder. Happened every time thr car was returned to idle, traffic kights etc. (when clutch depressed)  took the car out this afternoon, went to buy a new thermostat. Car ran sweet, no issues at all.
Any ideas on what could be causing the rough cold running?
Also how loud should the turbo noise be? I can here a whistle/whoooosh..... Its not loud, it comes on boost ok. Having never driven one of these engines i'm not sure what it should or shouldnt feel like.
Future plans are coil packs and plugs, also considering a smoke test to spot any leaks that might be present

[barrym381]

what year is the car 

[navmk4gti]

Get a vagcom cable of the bay and scan it for fault codes.

[dom]

Mine has an intermittent cold start problem as well, sounds similar to yours.

First thing in the morning it starts, idles fine, when I pull off revs drop and car feels like it wants to stall. A quick blip of the throttle usually sorts it, I've scanned it with Vagcom & no faults are showing

[barrym381]

Mine has an intermittent cold start problem as well, sounds similar to yours.

First thing in the morning it starts, idles fine, when I pull off revs drop and car feels like it wants to stall. A quick blip of the throttle usually sorts it, I've scanned it with Vagcom & no faults are showing

was your car part of the re-call for coil packs