When I fitted my boiler with the pump before what happened was ...........
First thing in the morning on a freezing day the callibration would be too low with cold water in the system so I'd recallibrate. When the hot water came through the hoses would go supple and swell so the pressure needed backing off - not something you could do in a hurry with a digital controller. Pressure built to the point of blowing the pressure relief valve in the boiler, so I sucked through the boiler rather than pressurising it. To be honest I found a gas boiler a pain in the arse, inconsistant temperature, too hot at times going out other times just not worth the hassle. On top of that was the insurance worry, running out of gas mid day, changing cylinders over and risks of gas leaks. Just didn't seem professional to me.
Since removed it and it won't be going back in.