i had same problem with my mk4 efi ,but mine was worse,i replaced electronic pack,ht leads,plugs,but i adjusted my fuel pressure regulator,so i didnt know if it was that,so i changed it and the choke sensor thing on the efi system as mine seemed worse when colded,after all that i started it up and it was the same left it running for about a minuteand it was perfect,i heard after new regultor or adjusting it u have to wait 30 second for it to set.pissed me off though