Isn't the OEM wheel a 20x7.5? If that's true and my math is right a 20x9 et40 would be ~ 10mm further inward than a 20x7.5 et49. Offsets are based on wheel centerline. So, offsets on wider wheels aren't comparable to stock. Also, I believe higher offset pushes the wheel further inward. Maybe I just misunderstand all this offset stuff, lol. Bottom line, just be sure you double check fitment with your wheel supplier before you order. Audio City was awesome with my order. They spent a good bit of time explaining all this to me. Hopefully I'm regurgitating correcting.
P.S. ET35 on a 9 inch wheel is perfecto!