I have a transgo in my 96 and love it-mine will bark a long second, jerking it sideways on bone dry road, and i can easily get a healthy chirp in third-all around 5800-6000 rpm at WOT-if I am NOT heavily on it but not driving like grandpa, 5000 sounds normal, shifts are very crisp too at any throttle.
If you are going to get on it on a fairly regular basis, I suggest you have a decent sized cooler, but that sounds pretty normal to me.
I also note that you said this happens when the trans seems to be cold-higher line pressure might be the reason it doesn't seem right, what is it like warmed up?