So my b16a1 will start up alright when cold but idles really low like 1000 rpm for a couple of seconds then wants to die. I have to use the throttle to keep it alive for a minute or two until it's stable then it idles fine, though between maybe 700 and 1000 rpm and goes up and down a bit aswell. It sounds like it's not getting enough air or too much fuel since if it dies it struggles to start back up if I don't help with the throttle a bit.

could it be that the 02 sensors are mixed up? should cyl 1 3 go to c16 (bank1) and cyl 2 4 to c8 (bank 2) cause I might have mine mixed up or are the 02 sensors even used during a cold start?
Or is it maybe the fitv?

runs fine when warm

 

It would be open loop at cold start, so O2 sensors won't be involved.

I would suspect the FITV/IACV, there are ways to test/clean them. I don't have a FITV engine so I can't really say how, so you'll need to do some research.