When speeding up on the highway, especially when going up hills, feels like gas is cutting out to engine.

Have you checked your air filter, fuel filter and spark plugs? Is check engine light on?

Check engine light is on but the code keeps coming up as my neutral safety switch but i replaced it and had it reset and it came back on a day later with the same code. The fuel filter was my first thought also but the filter is part of the pump module in the tank along the the pressure regulator which was my second guess.... The spark plugs look good. I will check the air filter though and update in a little.

Are you sure that the trans is down shifting as it should when you pressing the pedal to the floor? Kinda sounds like it might not be down shifting properly.

It feels like it is and the transmission was just rebuilt within the last 8 months

It's definitely a gas problem because replacing the fuel pump made it a lot better but the problem is still happening, just much less intense.

Could be trash in injectors or fuel rail. If you use 87 octane it can cause issues. Flush your lines and see if improves and clean injectors