yeah, thanks for all the suggestions and comments...
i will check if there is any air leaks on the connections...
how to get remove the oil on the maf sensor if it was contaminated?
in additional, after i switched to N at about 120km/hr, the tachometer needle dropped to 0.5 rpm only, is this normal?
like after 2 or 3 seconds it popped back up to around 1.0 rpm.... so in this case, it could be wrong reading and cause the engine stopped?!?!