Overheating issue on KA rebuild - need your help

[OverBoost]

Guys, I have an overheating issue I just can't seem to solve. I have a recently rebuilt (less than 100 miles) KA24DE that overheats after about 15-20 minutes. It is completely stock except for a barely used Mishimoto SR radiator with crossover pipe and electric fans. It does have a new waterpump, new thermostat and new hoses.

I have completely bled the system twice, with the rad cap off, funnel in to watch levels and I made sure all air bubbles have come out of the system (also turned on/off heater in the car). It currently has 50% water, 50% coolant and I have also added Water Wetter.

When idling in my garage the temp gauge stays right in the middle where it should. When I close the hood and take the car around the block, it starts to creep higher and gets almost all the way to the highest H mark. The top radiator hoses are very hot but lower hoses are cool/light warm to the touch. The hoses also seem to be under pressure as they visibly expand when hot. There are no leaks/drips.

Could it be a bad temp sensor (near water outlet)?

ANY ideas would be very welcome as I am stumped. Thanks!