First off, over-inflation is just a bad as under-inflation, if your running you Michelin's at 40 psi that's too much, they are overinflated.

What ever you do , do inflate them to the pressure listed on the side of the tire, that's the max pressure as recommended by the tire manufacturer.

And no, the placard in the door is not meant for the stock tires only, that is the recommended pressure the vehicle manufacturer specifies for the best overall performance and handling and fuel mileage.

36 is perfect , leave it them there and enjoy a nice ride and long tire life.

BTW, are you running nitrogen in them?