Hi, thank you for the feedback.
No modification on my bike yet, including exhaust, using standard one. I felt this problem since receive the brand new unit though.
Did ECU scanning and no malfunction detected. May be the MAP cleaning will be the next step.
However, did change the spark plug, ignition coil, swapping full set throttle body, fuel pump, cleaning air filter and new fuel filter, this problem remains. Any idea what next to check?
Wondering about ECU. Is there anyway to reflash the ECU? In case of faulthy programming or something.