I have done the searches, so I have seen what the velocities should be. Probably best to see the condition of the seal also. I have a compressor and have taken apart a few guns. The 3 ball setup doesn't look too troublesome, but can this also be left in place by using a shorter slave/dummy pin, and removing it all in one piece? This works well with the M34 T05.
I just felt the 27 shouldn't shoot slower than my other smaller light powered guns, although accuracy and smoothness is the first priority.