Truck upshifting too early?

If the truck upshifts too early is this becaue of the tune?
For example, when I am cruising then floor it, the truck will downshift and the rpm will raise to around 4-4.5k then upshift sudennly. Why is this?

Thanks in advance, Mark.
http://www.cardomain.com/ride/2081389

The wot shift points aren't high enough or the downshift points are too high.
This will cause the trans to downshift, then immediately upshift.

allen

I will call you about modifying my tune on Monday then Allen. Or do you need any more information about the tune? Well actually, my speedo is still not fully correct. If says I am going about ~2-3mph faster than I really am, as I mesaured it with my GPS. ANd I also finally added my Thorley headers and dual exhaust if that matters too. I noticed the shifting being like that after I put in the headers and exhaust.