I've been hearing alot more noise from the LS over the last week. I had my windshield replaced (due to a crack) a couple days after I initially heard the noise but even after changing it out I still hear it. My ears can't pinpoint it but I think its coming from the rear of the car and goes up and down as I accelerate. Sounds like I have an aftermarket exhuast or intake on the car now. Any clues as to what it could be??