High tickover

[johnny]

My Silvia is suffering from the dreaded high tickover but only when warmed up, cold is around 800 rpm and warm around 12-1300 rpm. After searching through the forum it seems this could be caused by an air leak. Is there any way to check this is the case by removing and blocking a pipe etc. On mk1 Escorts I've had in the past we sprayed wd40 around areas we thought might be leaking air and the tickover would alter if this was the case, would this work on a more modern car such as the Silvia?

Or could it be something else due to it only doing it when warm, a cold start sensor not turning off or bad connection? Or is there simply a screw for altering the idle when warm.

Sorry for all the typical newbie questions