Funny noise??? My 2003

I have a 2003 Frontier supercharged. I noticed since last weekend, I started hearing an electrical buzzing sound, for the lack of a better description, when I step on the accelerator. It only happens when I begin to step on the accelerator, near the top end, and when the truck is in drive, as opposed to being in park. It only has 20k miles so still has plenty of warrenty left. When I took it to the dealer to have him look at it, they said they heard the sound but didn't seem to think it was a big deal. Does anyone have any thoughts on what might be going on? Thanks in advance.

I've had to tighten down some heat shields under the truck before that cause a buzzing noise at certain rpms. other than that you may just be hearing supercharger whine and hiss at high rpms since they aren't intercooled they tend to make more noise when revved!

later,