Dear OP,
This is incredible to me!
I drive a black 550i GT with sport package and 20" wheels. I drive in the city; rain, snow; rally style, stop and go, 110 mph; drift and pretty much anything I can imagine. To date, I have added air 5 times in one year to my run flat goodyears after 15k miles and I still have over half the treadwear left.
I cannot understand what is wrong with your tires!
I guess as car fan says, change tire type or something!
Also, the TPMS or valve stems could be leaking! Wow this is probably it. They could just be defective. The full TPMS system is about 60 dlls per wheel. Why not get the Hankooks and new TPMS and see what happens?
That white GT is beautiful. The 3 series feels smaller than my beloved, bulletproof VW R32. I would shoot myself before trading my GT for a 3 series. Well, unless it was for an M3 sedan.
I really would. The GT is so royal and unbelievable. It is like a beautiful princess with an unbelievable 6' 2" physique. Why would you trade it for a 3 series coupe with a sardine-can sized interior????? My R32's interior is huge compared to the 335is.
Consider to change wheels, tpms and tire model before getting rid of that gorgeous white GT. That is my honest opinion. And I would start with the valve stems in the TPMS. Those are 10 bucks a piece.
Good luck!!!!!