I have vitz 2004, 4 Cylinders. From Last month i was observing that my vitz is not goin on 100+ speed with AC even without AC it goes on 110. It was giving me very good fuel avg 13+ in local in 14.5 on long before i made some changes in last three months.
1- Change gear oil use GS Oil not use Toyota orignal this time.
2- Change Tyres New Dunlop 185/65/14 (I already have 14 inch rim installed only tyre change)
3- Change Plugs spark plugs to iridum plug.

Now i have made these changes in last three months. I have to go to islamabad and became to know that my car is not going above 110 with full acceleration.
i have do these changes again to solve my issue.
1- Installed spark plug again (nothing happen)
2- Go to tyre shop and discuss every shop keeper said they never heared this kind of issue came from tyre change.
3- Change air intake sensor (Nothing happen)
3- Wash silensor (Nothing Happen)

i dont know what to do now. Pls guide if any one know this problem.