Idle/rev issue when cold
 

Hi all,

I've got a 2004 WRX JDM wagon.
Been having an issue recently that's slowly happening more often.

Start the car when its cold, car sits at around 1500rpm which I've been told is normal.

When I go to drive off the first 30 secs to 1min the car will just hold that rpm, if I depress the clutch the rpm will climb to around 2000, drop to about 1500 then back up to 2000 again.

Issue goes away after a minute or so of driving but I don't know what would be causing it.

Car also seems to idle quite low at around 650rpm, or 700ish with air con on.
If I go to pull away there is hesitation from the car, goes to stall and then rpm jumps to about 1000rpm and it pulls away.

Any help is greatly appreciated.

Thanks
Nick