Bro.. First of all I think you made a mistakes on calculating your FC. Do you mean 7.8km / litter? If that is the case, then the more the better because for every litter of Fuel you go longer distance.

If you are saying 7.8L / 100km then is different case. If you're having 7.8L or in fact 8.6L / 100KM. You instead have quite a good consumption with only 0.14 and 0.16 cents / KM using RON95 which is a good thing - Almost like Vios FC.

please check whether they change the the same rating oil coz factory fitting oil is mineral 10w 30.

2ndly, check whether u r checking the average fc@instance one, n remember to reset it coz the reading will be average of since day one unless u reset it.

3rdly, just probability, even with same driving habit n route, but its not the same idling time coz idling time also can cause up to 30% diff in fc(including idling at traffic which not the same everyday), so,there willl be a plus minus for every fc.1 to 2 litre plus minus, is normal.

4thly, another way to get better mileage that even me dont do it nowadays is to wind up windows, driving less than 90kmh :-). Have u guys try this out in cfe? Its efficient, but not comfortable. Thats why i never suggest this method. But for fun sake to check how much the compressor take out the power n fc, give it a try for a full tank.

there's a recall on driver side power window coil spring???...different than the previous power window regulator right?..

If the steering vibration appear after 100km/h even with good tyre balancing/alignment (rotation doesn't matter, its about evenly out the wear and tear), it most likely have to be uneven wear of the tyre. Try visual inspect the tyre yourself, if the uneven wear is serious, u can easily notice it.

When was the last time you had tyre balancing and wheel alignment?
To get more confirmation, get someone who are good in spotting it out and check for you. Else, snap a photo and upload here.

Hood insulation? Surely you can but I would go for third party sound/heat insulation instead. Cheaper and should be more effective.
Eg, something like this. https://forum.lowyat.net/index.php?showtopic=2262458&hl=
* I would go for Syntium 3000 is budget allow. Its much better than Syntium 1000 in term of performance.

Ask for 2nd opinion.
Send to another shop for wheel balancing, see what they comment on your tyre.

I want to know if u have tyre uneven wear issue, if u have, vibration is NORMAL.

guys lately my car idling rpm abit low and sometimes engine dies on low speed probly 5-10kmh

anyone experiance this ?

and the fc suddenly goes so high... also when i rev the car hard theres white fumes coming out from aircond loli