Unit runs fine on flat level but when going up a ramp it struggles, it won't move forward as if it has lack of power. When adding more then 20 in-hg of vacuum to the diaphragm on the distributor, unit goes up the ramp with no issues. I also inspected the vacuum lines, they look good but I don't know if I'm overthinking but does the diaphragm need to be replaced or I need to look somewhere else? I've been in the forklift industry over a year still learning. Also not that familiar with Toyota fork lifts, is there any other test that can be done to confirm if the diaphragm is bad or what's the proper vacuum?