Update:
I installed steel trigger with Wolff TCU (standard power) + Elite II hammer. Polished all metal parts with 1000 grit sand paper including trigger, Wolff TCU cam, trigger bar, hammer, hammer strut.
Man, what a great improvement !!! The DA trigger pull is perfect, lighter than on my Sarsilmaz Mega, and SA trigger pull is very crisp with reduced reset travel (but a bit heavier than SA trigger pull on Sarsilmaz). I tested these upgrades at the range, shooting 200 rounds, including 50 rounds of IMI-DiCut. I never had good accuracy with IMI-DiCut before, and now I have 3 inch groups at 30 feet!!