While troubleshooting my engine yesterday I decided to listen to my injectors with a stethoscope and a couple sound like they are screeching... like an old 300 baud modem. I'm pretty certain that's not right. The majority of them sound like a nice oiled sewing-machine hum and click.

Actually.. they all were fairly noisy at first, but most of them smoothed out while I was monkeying around. I did put a can of gas treatment in the tank earlier that evening. But perhaps that could be coincidence. However, the miss I was experiencing seemed to go away as well... and no noticeable stumbling on revving. I didn't have the time to take it for a road test last night, but I will today.

Can anyone confirm what the injectors should be doing / sounding like? I don't imagine the sound of them should change much during operation. And I also assume they should all at the very least sound the same.