(y)...Nice questions. I will try to answer the top 10 of the list: 
Ans 1. Fuel Guage Problem. Cost around Rs.1500/=
Ans 2. Brake pads worn out. Cost around Rs.850/=
Ans 3. Door hinges are too loose. Replace. Cost around Rs.800/=
Ans 4. Windsheild corrosion and need replacement. Cost around Rs.4500/=
Ans 5. VTEC was not put into diesel pump for LC. If need to put, you need a expert electrician....
Ans 6. Due to lighter weight, the Mehran lifts up a little bit from the road thus not transferring any power to the ground any more....
Ans 7. Your Type-R Sticker is lacking a dash that's why it is not giving an optimum performance.
Ans 8. Certain Corolla 2.0D came with 20V engine but later they removed few of the valves to improve fuel economy...
Ans 9. No, don't use hi-octance since they will badly effect the spark plugs 
And 10. Next time try shifting the gear to higher one when on motorway, it seems you are not going above 2nd 