hmm..all your pick up is there? i see..is it, engine rasa kuat or pegi rasa cepat? from user manual, u will reach 0 - 100km/h in 12.4 seconds, compare to 1.5 engine which is 12.1 seconds..if your engine stock, just the gbox been change, try drag race a standard 1.5 wira..if u win, confirm your flywheel is lightened..standard 1.6 got top speed of about 190km/h from user manual..meaning from mid to hi better than 1.5..contributed by the heavy flywheel..but at low rpm 1.6 engine supposed to feel underpower/soft a bit..
btw, i also been playing with the distributor..(u didn't state it runs on what ecu, so i just guessing) from my experience, if too advance (but still below engine knocking range) less top speed, but better torque..this factor can also contribute to engine rasa kuat..but pergi rasa cepat wise suffer a bit resulting less top speed..if to retard (but above knocking range) no top speed and no engine rasa kuat feel..too advance and too retard is easy to know, the fuel gauge drops like crazy when accelerating hard..but for too retard also got one symptom, the exhaust sounded like rally car when rapid release of accelerator pedal..(the sound that u can see fire out of the exhaust) and also, u need to rev the engine harder to get the power needed to move and accelerate..resulting higher rpm a bit..when i set my distributor a bit retard, i got 100km/h at 3200rpm compare to now which is 100km/h at 3000rpm
errr..6.5krpm only got 170km/h? didn't notice this one..go check the meter, then all the sensors..if u can explain more about how the car feel when u drive, maybe the sifus here can help..
p/s : emmm..auto gbox for 1.6 is controlled by ecu (it have transmission control unit) right? from what i understand 1.5 auto cannot fit 1.6 auto gbox due to this reason..meaning it is not as simple as changing a 1.5 auto gbox to manual which is just like plug and play because it's mechanically control..try asked the mech back if the transmission control unit has been disable, or can be disable or need to change the ecu to manual ecu..