Finally manage to secure a place where i can leave mango on tripod for at least a month's time for me to slowly do all the tweaking and overhaul his heart. As I had a sure feeling that one or more of it's cylinder is loosing compression.
As expected from our McGuyver, my 4age-20v is taken out from mango within 1 hour and taken apart in 2~ XD~ buggy fast he work.
And to our~ (mcguyver said it's his first time saw this kind of condition after so many 20v he had taken apart) HORROR~! cylinder one and four have this 'crack' kinda mark on it's cylinder and both piston ring were about 0.2mm smaller. Not sure it's a lot but it definitely effected mango's hours power.
So with the twist of event.... an engine block change is in evadable~ Good thing i had two more black-top block in spares~