Fuel flow testing

Last night I tried first engine start-up. Initial one second run and then nothing. Seems after some attempts I had no fuel.
In all my investigations I found a fitting at my Red Cube that still had a punch out stuck in the fitting causing almost zero flow. Fixed that now fires right up and runs good.
Here is my question. During my troubleshooting I did a fuel flow test before the FI servo but after the electric and mechanical fuel pump. With the electric fuel pump running I got a small amount of air. To me this means a suction side air leak. However I had no static leaks, same amount of air on either tank selection. This tells me that it is after the selection valve and before the electric fuel pump. Checked all fittings and no leaks and no change. Then I decided to shut the selection valve off to see if I get air. Nope. Nothing no air no fuel movement.
This tells me no air leak after the selection valve.
What gives. Will the electric Andair fuel pump cause some bubbles? Cavitation maybe?

Follow-up

I did not receive any responses to my first post so I thought since I now have the solution I would post.
My original problem was air or bubbles in the line while flow testing my new install. I haven't flown yet but have done first, second and third engine run without issue. So before flying I thought I better get a solution to the bubbles and I needed to empty the tanks for final weighing.
This time I connected a valve and hose to the hose leaving the primary fuel pump at the fitting just before the FI servo.
I ran the electric pump and sure enough got bubbles again with very good flow rates. So I started closing down the valve to help restrict flow and sure enough the bubbles went away. Apperantly these bubbles are fuel vapor not air (system air leak) and running the flow unrestricted allows the vapor to be created. With restriction it will not. I am now confident in my fuel system and almost ready for first flight.