I have a b16a jdm and i recently changed the head gasket.

the idle is not steady after i drive 1000 to 1400 but after a minute or two it goes back to 750.

at idle it makes constant white smoke out the exhaust. when i press the gas it goes away.

i am not burning a lot of oil or coolant then what could be the problem?

 

On a cold day with a cold engine, water vapor produced by combustion will condense to produce steam from the exhaust. Is this what you are talking about? Otherwise, white smoke indicates that coolant is burning in the cylinders, which suggests a problem with the head gasket. Perhaps the block or head was warped by overheating and not properly resurfaced?

Regarding the idle problem, try bleeding the cooling system and cleaning the IACV on the throttle body.

 

is the coolant suppose to to be low in my rad if its burning?