Vauxhall Vectra B 1.8 16v 2000 estate - Won't pull away when cold - bobcb250

I have a 2000 1.8 16v Vectra with aprox 112k on the clock, recently, it's having some cold running issues. Starts up straight away (I think it used to rev at just over 1000rpm when cold but now runs at normal warm tickover), but until the engine is warm if you try to pull away it stalls or misfires, if you leave it to warm up it will run all day without problem, it's perfect. I'm definitely no expert and by reading various other forums have carried out the yellow wire mod, replaced the plugs, ignition pack, maf sensor and coolant temp sensor, but its still the same. Any ideas please?

Thanks for your time.

Edited by bobcb250 on 08/03/2013 at 17:50