So I have installed the new MAF, changes the engine air filter, and fixed a minor air leak in AOS tube. Did not help at all. But the engine runs better at least

. Next coming up idle control valve. Also I have found an oil leak from the oil filler tube, looks like the tube has a crack in the middle section (the corrugated section) which can also cause a small air leak but I doubt that this is related to my problem.
One interesting observation - RPMs get stuck when I drive faster than 40 mph and will drop back to normal when I decelerate below 38 mph. I think it's the idle valve that does not close properly.