1. Best I can get on mine is 16KM/l (manual) and that is with a major condition to achieve and yours are still below 1k, it will get better eventually after first service

2. Vibrate like what? can clarify specifically?

the car should feel smooth... but if u mean it feels wobbly on high speed that's because persona is a tall car... with a soft suspension for a relaxed driving...not spirited driving... the car is meant for city driving..not hiway cruising.. on the plus side.. hiway cruising is still better than other car in its class..

back to the topic... the car rim is already 15 inch?.. 16inch with wider tire will increase the grip....

but if u feel a vibration on the paddle..that's normal on any car.. with exception of luxury cars

Perhaps due to the tyre pressure? When I pump my car tyre for the 1st time the meter reading is at 260kpa, I lowered it down to 220kpa. I do the same like u too, taking corner at 140km/h - 160km/h at highway, can feel the car not stable, maybe because of the soft suspension. U can modify it by lower down the car spring.

Talking about affecting FC, I don't think its significant enough you can see the differences.

Don't forget after your tire diameter got larger, you may need to add some to your mileage too when doing manual calculation because your wheel just turn slightly lesser for the same distance driven...

But anyway... its too insignificant that you actually don't have to care so much about it... Janji heppi sudah

When my tire worn out I may put up a 185/60/15 to see if the ride more comfy... and mayb speedo become more accurately reflecting the actual speed my gps showing 

Eh... I am no boss.. but I do agree with the meet up 
I duno how to friendly honk... today just saw one Premium beside me at Bukit Puchong bridge and suddenly think of this
but mana tau when cornering it came makan my lane... luckily I had an eye on it 
The rattling noise at passenger side from before has completely vanished.

But...

New rattling noise like somewhere in the stering or cluster meter appear pula 

But very rare occasion only... like today never encounter any noise

does your car jerk when its at low speed?mine is too obvious..did not like it as my previous car do not have this issue

thank you so much for the steps shared     

i will try this steps for a few days and share the outcome 

Anyone done soundproofing persona yet? Is it worth it?

Thanks

Newbie Question:

Can show/tell me which part of the car you did soundproof?

Thank you