I will second Umair2203 suggestion to check the Catalytic Convertor as it play's a vital role.
Symptoms can be poor engine performance , car achieving very low mileage.
You can try the product STP Fuel system cleaner or if you can source CATACLEAN
If you are going to Toyota garage the only glitch is they dont have a solution to clean out the Catalytic covertor other then breaking it a new Catalytic convertor is very hard to find plus quite hard to install. So the above 2 cleaners will really help you in fixing this low mileage issue.
Also just get the Throttle body serviced out & keep 30 psi in all 4 tyres.
All the best