I recently put a 4.5 inch lift on a 2001 xj and have been noticing an oscillating vibration noise that appears at around 45 mph and gets louder and more frequent as the speed increases. There is no change when coasting, giving it gas, or when braking. The vibration started occuring when I put on new 32 inch tires and rims and replaced the stock tires. The tires have been balanced (2 times to make sure) and the front has been aligned. There was no vibration noise with the stock tires. Any idea what the most likely cause of the vibration noise is?