Have an 04 with TranSynd filled about 50K, now 110K on truck.
Every morning I run it up at full throttle to about 65 to clean it out. The past 4-5 weeks it will not shift into 3rd unless I back off and even then it hangs up for a while. Did check the fluid and it was a little high so dumped the filter contents and looks OK now, but problem is still there. Find it usual that temp gets over 150, mostly runs at 130.

Do have a check eng light but assume that's the EGR again since it's warm outside (winter time it goes away)

Have an 04 with TranSynd filled about 50K, now 110K on truck.
Every morning I run it up at full throttle to about 65 to clean it out. The past 4-5 weeks it will not shift into 3rd unless I back off and even then it hangs up for a while. Did check the fluid and it was a little high so dumped the filter contents and looks OK now, but problem is still there. Find it usual that temp gets over 150, mostly runs at 130.

Do have a check eng light but assume that's the EGR again since it's warm outside (winter time it goes away)
I'm not sure what you're trying to "clean out", but how long has it been since you have changed your engine fuel filter?

Your symptoms indicate that the engine is down on power at WOT, so it can't reach the shift point and hangs until you back off. Most likely a restricted fuel filter.

Oil & filter and fuel filter changed 1,130 miles ago. Change oil/filter every 5K (100% synthetic) and fuel filter every 10K. If I keep my foot in it the RPM's go to 3.2+ and I back off - used to shift right there.
Mileage is still good, idle normal, can not think of anything working wrong besides the Vac Pump making noise.

Fuel Filter. Could have gotten some dirty fuel at one point.

The engine speed may be there but it's probably down on torque which is holding up the WOT shift. Change the fuel filter and go from there.

I'm not sure what you're trying to "clean out", but how long has it been since you have changed your engine fuel filter?

Your symptoms indicate that the engine is down on power at WOT, so it can't reach the shift point and hangs until you back off. Most likely a restricted fuel filter.

X2 don't really get "cleaning it out" more like abusing it

Sorry it took so long to try a new filter, but work inter-feared. Found what looked like a thin layer of paint in top of filter just floating there (quarter size). Have not been out early enough to make a good WOT run, but a few short runs at WOT - its back to normal.
Thanks !!!

As for my morning WOT runs - it appears to me that if I run around town for a week or so and then make a WOT run it pushes out a lot of brownish smoke. However after making the WOT run a few times that smoke goes away. Perhaps I'm just thinking of those gas engines but its a good excuse.

Again thanks for the simple solution.