I have some news..and good ones at that.
So i went to Toyota Experts near Gulberg. My cousin has a 2015 passo and he gets his car checked from there so they came recommended.
Turns out the car's race (acceleration?) was set too high, so he set it back to normal. When he did, the AC started tripping and turns out the choke was not working due to which the engine was not producing enough power.
I guess the previous owner took it to someone that instead of solving the issues applied local jugaars.
Thankfully there was only a wiring issue with the choke so he fixed and lo and behold that car started accelerating like it should and the average went up to 12.5 from Gulberg all the way to Scheme 3 via airport road.
PS: while the mechanic near me told me that the engine is weak, Toyota Experts did a compression test and told me its in good shape. They also scanned the car and checked fuel pressure which all came positive.
PPS: turns out i was a little too harsh on my brother's Friend..guess his expert opinion wasn't that bad after all. Still mad about the cat which might be a Rs40k hit at this time due to high inflation.