I was talking about the pressure line back to the pipe - that can get partially plugged inside pipe and then the pressure used to pressurize the tank is intermittent, it comes and goes. This would affect the way the fuel is feeding which could affect idle.

Case I've encountered - pipe plugged and engine was re-tuned to run, but when pressure would come back, it engine would see increased fuel flow and idle would go up until the pressure went back down.