Thanks for your answer.
But 33 psi is the correct pressure given on the sticker inside the door of the car.
Besides, I've always driven my car with 33 psi tire pressure more than one year untill they were pressured upto 38 psi.
Sorry to piggy back this thread but if you get new tyres fitted do you need new valves even when you have TPMS? I read they can last for up to ten years but most tyre dealers charge for new valves whenever you fit a new tyre.