ok, lets discuss this with a very open mind, no flaming.
ideally, the vios will never be able to beat your 1.8 wira. when i say ideally, it means good launch, car in good condition, shift up at the right RPM and so on. thats if you compare a exhaust mod vios like his and a exhaust mod wira like yours.
however in reality, nothing is ideal. for all you know the vios got some heavy modification under his hood and is in sleeper mode. its hard to judge till you see wats underneath it. besides, there's all these small factors u have to take into consideration. he might be on light fuel load, and you're on heavy load. he might have off his aircon to gain some acceleration. and one important factor, condition of your car and the quality of modifications in it. i've used some really fucked up extractor + bullet with bad workmanship and my acceleration sucks big time. very laggy!
and not to forget one very important factor, how early he started to floor the throttle. u mentioned u let him go and he showed u the thumbs down. chances are, the moment u let him by, he was already full throttling and that means when you cut back into his lane and full throttle, you're basically at least 5 seconds late and that explains why you failed to overtake him even at 170kmh. sometimes when i try to accelerate to prevent a iswara or kelisa overtaking me, i can't even catch up with them coz from far they already started acceleration and carry the momentum while you're only building it up.