Camry :: 2008 Engine Don't Idle / In Reverse, RPM Drops

I own Camry 2008, 4 cyl, 2AZFE engine, 2400cc.

I recently, started facing strange issues,

No matter whether engine is stone cold or oven hot, it does not idle where it used to be (2 weeks ago). The car idles at ~800 RPM and the rpm suddenly drops to ~700 and engine flushes in more fuel to rev it up to 1100 rpm. Will take another 10 - 12 sec to reach ~700 rpm and the same story continues.

This however, sometimes go away, in Neutral. Once I put it in Reverse the problem becomes worse with RPM dropping every other second, as if the current in the coils is failing.

All this fuss continues, even when car is at 30 mph. However beyond 30 mph I feel nothing.

Services done in last 2 weeks:

1. Throttle body clean-- complete removal of all the gunk.

2. PCV valve changed from toyota dealer.

3. Mass airflow sensor cleaned.

4. Spark Plugs changed with new Iridium plugs from toyota dealer.

5. New Ignition Coils.

Nothing solved the idle problem - missing in the car. The mechanic convinced me that Head gasket is blown. He was indeed right as the Head Gasket had crack b/w cyl 2 and cyl 3. It was changed and car was much better. But now I am again facing issues.