1-2 Shift Flutter

[RedFX4]

Hi,

I just got my Gyphon today and have it set to the 87 tow canned tune. My issue is that when my foot is to the floor, literally, the truck will climb rpms to what I imagine is the typical shift point, but when it goes to shift its sounds/feels like it slips out of gear winds past 5200 and slams into 2 gear. I understand the tune firms up the tranny but this can't be normal. Kind of does it in the 2-3 shift as well but to a much lesser degree. As long as I don't put my foot to the floor and hold back throttle a bit, it doesn't have this problem and shifts normal, nor does it have any shifting issues in daily driving.

Is this normal or has anyone else experience this issue?

The truck is stock aside from a magnaflow catback. 2008 FX4 5.4L 3V with 3.73 gears.