I have pinholes in my Model 240 or 340 DucTester flex ducts.
One question we get a lot is about leaking flex duct that connects the ducTester to the return. We have tested the most ripped up flex available in our warehouse; it had way bigger pinholes and it measured 0.68 CFM at 25 Pa. When you measure a typical leakage of 100 CFM at 25 Pa or more, this is not even 1%. So we believe it is not worth spending money on replacing.