Overall diameter aside, even though your 19" wheels are lighter than that stock 17" wheels, the weight is further out from the center axis. Try taking a 20lb weight and spinning it. Then take that same weight, put it on a 5ft pole and try to spin it again. It's a lot harder.....

And, like everyone has stated, your tires are WAY too big! The stock 225/45-17 tires have an overall diameter of 24.97". Your 265/40-19 tires have an overall diameter of 27.34" - that's a difference of 2.37"!!

Let's say your speedometer reads 60mph with stock size tires. With the tires you have now it would read 54.7mph, even though you're still at the same speed. Now you speedometer is 5.3mph off, not uncluding how for it's off stock (which is normally ~4mph at that speed). You're almost 10mph off now!

When changing tire size, it's recommended that you stay within 3% of the diameter of stock tires. Your tires are 8.67% larger

If you like your 19's try buying tires that are 245/30-19. These tires have an overall diameter of 24.78", which is just slightly smaller that stock (difference of 0.77%). At 60mph, your speedometer would read 60.4mph.