I was having the same issue with N430DP this summer. I had it removed and sent to the prop shop for bench testing and had the springs replaced. They ran it for 2 hours on the bench with no issues, but I’m still only reaching 2600 RPM on takeoff.
I have the same problem, but my A&P thinks it is related to the linkage to the governor. Like it is not long enough to get that extra 100 RPM and will need some modification. I am going to address over the winter.
We adjusted low Pitch stop to maximum but no RPM rise. The linkage itself is quite simple to a adjust, but that is not the problem. I will measure the low pitch angle to check for a wear of the propeller. Last overhaul was 2009 and last maintenance was 2020, lubricaction of the hub.
A month before my Mitchell tach showed a malfunction, an overspeed on take off of 2900 rpm without a change in pitch tone. The new tach showed only 2600 and then 2550 on takeoff.
I will keep you posted…