Andy03STI

I have a problem on my 03 Sti. When it's cold and gets to about 2000rpm car runs terrible like it's missing. As soon as I get a mile down road and it's warmed a little it's ok. Then when it's warm and you turn at a junction and accelerate normal it does same problem. Some days it starts cold and drives fine even when warmed up. Also if you pull away brisk from lights sometimes it stutters before it goes like you havnt put enough revs on and let clutch out too quick. Had it plugged in twice now and sods law each time it's behaved and everything is doing as it should. Just wondering if it's possibly neutral position sensor or any other ideas. Thought could be a coolant sensor but can't see that causing problem when turning and I hear lambda would turn cel on. Also checked all connections in engine bay all seem fine.