I thought it was my tranny at first because I had just installed my transgo kit. I thought I had messed something up. But I later tracked it down to being my belt was slipping becasue of all of the black belt dust around the alternator. I still get a little squeek from time to time but nothing like before. This was all before the whipple.

 

Just under WOT in 1-2 and 2-3. It is VERY noticable, louder than the exhaust & tire chirp.

 

I have the exact same problem on my VHO. I have 11,000 miles or so now, and it has done it since day 1. Only on 1-2 and 2-3 shifts over 5K rpms, so i don't hear it too often, but it is very consistant. I even told the service guy about it when I got some other warranty work done, but they gave the truck back with no mention of the problem. Kinda weird trying to explain the problem since it only occurs at such an extreme rpm.