Na. Here's the deal. What is most likely happening is you have some leakers. When your idling, the fuel pulses are moving more slowly, and the pintle is being lifted off its seat slower, and not going up as far, so the spring doesn't slam it down into the seat as hard. Here is what happens... for the sake of discussion, lets assume the first injection sequence goes ok. Fuel gets injected at the right time and you get a smooth cylinder fire. As the ignition occurs, the cylinder presures go way up and the pintle lifts slightly off its seat due to a weaker spring. A little bit of carbon slips in and holds the pintle up ever so slightly. There is a slight amount of fuel presure still in the injection line, so as the power stroke ends and the exhaust stroke begins fuel is starting to bead in the seat. A droplet forms and falls into the cylinder. Now you have insufficient heat to ignite it completely, so it burns off as low temp smoke (blue haze). Now the intake stroke completes and the compression stroke begins. At the appropriate moment, the injection pump sends fuel under presure down the line to the injector. BUT... some of the fuel is missing. The presure needed to pop the pintle off its seat is missing, so the pump injection sequence ends before the presure needed to lift the pintle has been achieved. Or if it was achieved at all, it was achieved late, and a smaller fuel delivery occurs resulting in a weak firing cylinder. Now you have a bump in your idle. The cylinder strokes continue, and maybe the pintle is leaking again like before, or maybe not. Maybe the next ignition occurs and the stars are aligned and you get a valid properly balanced ignition, and then maybe you don't. So you can see with a leaker you get uneven unballanced power strokes. As fuel delivery and engine speed increases, the sealing characteristics of the pintle start to change, and you can end up with an injector that is working fine producing a smooth running engine. But when things drop down to idle again, the bad injector characteristics re-emerge, and drive you crazy.