They should be the same psi it says on the door jam reguardless of which wheel or tire it is. I THINK the sensors are part of the valve stem. Again my car doesnt have tpms. So just to clerify you had those rims with different tires on your car and there wasnt a light, but then you had new tires put on those same rims and now the light came on? Or you got new rims didnt put them on your car until you got new tires and when you put those rims on the light came on?

 

Honestly at nissan we had cars come in with tire pressure light on reset it with a tool free of charge in like 5-10 mins and sent you on your way. But where did you have the tires put on? Maybe they changed your valve stems.

 

Quick fit done them so I'd assume they knew what they where doing, I really don't wanna go to audi they charge 80 pound just to put it on the computer is there anything else I can try before I go to audi