Is there a Schrader valve at the end that goes in the spark plug hole?
Mine has one with a long hose and I get perfect compression readings of 145 on my QT50.
With the pipe and kit I'm saying your jetting needs to be richer.
I was surprised with how much bigger my main needed to be.
I have jets from 70 to 130. 70 was stock and now I'm at 115.