Strange high rpm miss

[pnhigg]

I have a 5.3 T56 conversion in a 92 full size. The truck has had the engine transmission in its current state for a few years and has been 100% trouble free.
Recently if I pull hard up to 5000 or so rpm then shift the truck feels like it hits a wall and has what seems to be a miss for a second or so then pulls out of it. When it revs back to 4500-5000 rpm then shift to third same thing.
If I free rev the truck to 4000 or so then catch it at 2500-3000 rpm and hold the throttle there it will miss for a couple seconds then clean out.
No weird sounds. It idles fine, pulls hard off idle all the way through the rpm range , just seems to hit a wall at the gear change.
engine is stock with a cam and nelson tune. specifics are in sig.

thanks in advance for any help
Patrick

[pnhigg]

I have a scan log from hp tuners, but I am such a novice I don't know all of what to look for. If anyone would be willing to help I can email it to you.
I can't seem to figure out if it is possible to post to log here.

thanks