Ahhh... it makes noises when you let off the gas. I would say that is common, but sinse I know what all went into your lift I still suggest you buy longer LCA's to replace the stock ones. 3" lifts need them, and it couldn't hurt to have them with your 2" budget boost. I'm thinking that it is a driveshaft angle problem. Without the longer LCA's the front axle is twisted forward, making an awkward angle for the front driveshaft.
Now, if it only happens when you let off the gas, then that is fairly common. My jeep does it, and I've heard of many other people's rigs doing it as well. I think it has to do with the play between the driveshaft and the transmition. Have you ever noticed that when you put the Jeep in park it still rolls forward a little? That is the play I am talking about. When you let off the gas the pressure is released from the driveshaft and it starts to vibrate around a little. I wouldn't worry about it much, just one of those strange Jeep sounds that you have to get used to.
