EJ205 Turbo - RMPs first seconds after the 'hot' start
 

Hi guys,
I just recieved my freshly imported Forester 2006 with EJ205T engine. Engine is working great, however, there is an issue with RPMs:

When the engine is already hot (was running and turned off) and I start it again, RPM arrow rises to 1000rpm+ and next second falls down to ~500 RPM (or lower) and fly up to ~750 right away and then stay stable until the next re-start.
At the momemt RPMs reach the lowest point for a second - Oil indicator is on for a second and engine is about to stall.

I replaced the air filter (old one needed to be replaced for sure) and cleaned MAF sensor - as the result, RPM do the same dive and rise now, but the lowest RPM point is just a bit higher and the Oil indicator is not on anymore, but anyway, engine sounds working rough for a second before RPMs stabilized.
Car has 60k km on odometer.

I am thinking to remove the trottle body and clean it in and out. What do you guys think? Could I remove idle RPM sensor and clean it as well?

Please advise.

Thank you.