wierd sounds on my 99 PSD

[weewane]

First off I am new to diesels trucks, just bought my first PSD a few weeks ago. It has 135k miles on the truck. It has the stock muffler removed and a 4ft piece of 4inch pipe added and thats it. I did a DIY intake, and there is a superchip 1700 installed on the offroad tune.
So onto my sounds I can clearly hear the intake sucking in lots of air, the turbo spools up fine and has a nice whine/whistle sound up to about 2700-2900 RPM then the truck seems to fall on its face and I hear kinda a weird noise sounds allmost like a loud Kazoo, then the truck up shifts the wastgate opens and I hear alot of turbo whine which I guess is the turbo spooling down and then the power comes back on and everything sounds fine again.
Any idea what is going on? does this sound normal to you guys? What RPM should the truck pull to when it is pinned to the floor? Thanks for any help you can give me.