I just purchased the car with 20" EXE Konvex wheels
20X9 Front with a 245/30/20
20X10 Rear with a 265/30/20
I am unsure of the offset but it sits like a 4x4 because of the 30 series tires
so I need to lower it or change the tires

The problem is the previous owner said Discount originally installed 275/30 in the rear and 245/35 in the front (which would have been perfect) but it rubbed so Discount tire changed them out instead of ordering the proper offset.

How should I correct this?
What is the correct offset for a 20x10 rear and a 20x9 front, I would like to use a very mild lowering spring but dont want a tire rub.

 

Your offsets aren't that low so you will be good with a mild drop. My next tires will be a 255/30/20 on a 10 so the 265 that you are running is fine.

 

I just found out my offsets
front 35
rear 37

Can I lower with these

 

Should be a non-issue with those offsets.