Are you getting full manifold pressure on takeoff?
There's another possibility - was the prop worked on? If the low-pitch blade stops are set too high, you have effectively a fixed-pitch prop on takeoff. The fact that cruise seems normal can be consistent with this.
I once sorted out a prop with the opposite problem - takeoff was OK, but the governor could not control the cruise to the desired RPM. We had to re-index the high pitch stops.