Yasir
Regarding the car's height, I got mine's rear springs changed to slightly stiffer ones from khi. That took care of the issue pretty well. Car doesn't look raised which has been reported by people who install spacers. More on this issue (various options with pros and cons) on earlier pages.
Regarding most other issues, get your car serviced and checked from a good place. Might need plugs replacement, throttle body service, fuel filter clean up, etc. Killervtec, you might also need to go through this.
Yes, dirty AC filter affects the cooling. Also, don't clean that filter with water. In any case, from what I've seen, Vitz AC is not one of the best but does the job well. Maybe that's the reason fuel economy is not much different with or without AC in Vitz's case.
Aliakniazi
I invested in a maintenance free Bosch (Asia Silver 40Ah) almost an year ago. Seems to be working perfectly and as good as new till now.
Akif
Good to hear of your performance increase! Can you tell exactly how much the ATF level was earlier and is now and whether you checked on a started cold or hot car?
hsumbal1
Nice car. I have been getting car's engine washed with water for a long time. No issues. Ofcourse, care should be taken with engine, whether it's washed with any oil or water. I've seen that oil causes more dirt to stick and causes more harm... so I get water sprayed last.
The_Pretender
Check out the pic for my solution to the FM radio issue.
shamz
Good info on cat removal and royal shield polishing. Do they also apply on the bumpers? I have recently polished my car with Formula1 Wax (with micro polishing agents) hoping that it would take care of the minor scratches. Car looks great (shining when clean) but the scratches are there exactly as before! Did royal shield take care of the scratches too?
softouch
110 on CNG is okay (with O/D). Assuming there isn't any maintenance due, if you want to check car's speed, then do it on petrol. If it's fine, then all you might need is CNG tuning but that might reduce mileage.
happymaza
Nice car. I get oil (and filter) changed after 5k kms. Air filter ends up getting changed almost 3k to 4k kms... gets too dirty. You don't need any regular tuning. Just get the regular maintenance done whenever it's due.
khiites
Great get together! Good to see growing vitzers! About 2 years ago, there were already so many vitz in Khi that at times I saw a silver vitz right ahead as well as behind me with another vitz in sight! Yesterday, the same thing happened with me in Islamabad (3 silver in a line and a red one in sight)! The japanese must be wondering... "where have all the vitz disappeared???" 
All
Just got the mileage checked. It's giving me 13km/liter... so am not getting the cat converter removed. Don't want to add to the pollution until I'm left with no other choice! Note: when I got the car about 2 years back, it was giving the same mileage then too!
Also recently got a security alarm installed with remote start up feature (for engine warming). All knight rider fans would like this!
The attached pics show the following:
Seat covers - Tried to maintain the original pattern with different shades of gray. Didn't turn out as expected... as light shade looks almost white in the car.
CNG cylinder - Just to share that the spare wheel (with jack etc.) is in its original place with the cylinder installed this particular way.
FM Radio solution - Self explanatory. Another benefit is that I can use this for hands free too. Car speakers work as the speaker... very useful for group conversations.
Steering cover - Got it replaced recently... so thought of sharing that as well, while i was at it.
That's it. Take care. Remember to drive safe and not to blind the oncoming traffic with high beam! (pleease!)
