When I go for a test drive on my 1UZ swap I have an issue that I can't seem to figure out. Coming out of my house is a slight downhill. I can drive it the tenth of a mile down the slight hill and have full power and RPM's up to redline of 6500 RPM. When I turn around to go back home the slight up hill creates an issue. It has decent power still until I get to 4K RPM. Then it just stops reving or doing anything no matter what my throttle position is. Once the RPM's dip back to idle speed it will rev back up to the 4K. Once it hits that under load issue it continues to do that no matter if the car is under load or not anymore. It seem like something sensor or electrical related and not fuel pressure like I originally thought. Any help is appreciated.