Max speed
Well the answer is NO in mho !.
I fly very often high and fast (over the alps FL 85 -105)
A R44-I starts running out of steam, the manual allows you to pull full trottle, but raising the collective at some point doesn't help because the engine can't follow. As long as you would keep RPM you are OK, but the limitations don't take the RPM drop into account (an omission I think)
The R44-II doesn't suffer from this power hole.
d3