Injector cleaning is not really necessary if they are not creating any issues. Never had them done on my Civic.
At the risk of getting flamed, I recommend at least maximum sidewall pressure for maximum fuel economy. Tires that are commonly used on the Civic have a max sidewall pressure of 44 psi. This pressure is for cold tires, i.e. the car has been driven less than 1.6 km before pumping up.