your bio says 2007 3.5L CrewCab, so I'm sure it had the higher t-stat to begin with, that said ... I've been dealing with a very similar issue for over a month now, a few things come to mind to check …
Are the hoses really hard to the point you cannot pinch them together? indicates possible air or stuck closed t-stat …
Is the bottom hose really cold?
Air in the system causing the t-stat to not open? (a coolant burping kit works great)
At least 50/50 antifreeze ratio? a higher antifreeze ratio will make it run warm and not let it dissipate heat efficiently
Turn the temperature selector to the red (hot) side, you don’t necessarily need to put the fan speed on, this lets the water circulate thru the heater core …
Once hot, the needle should move down then back up under heavy acceleration, I wouldn’t do this test on WOT since it seems to be running on the hot side already …
To help cool off the engine, turn the heater on and fan on high
with the heater on, it should blow hot air out the vents ...