tach is freaking out

I had them in the 360 that was in my Scamp and my tach started bouncing at idle and it wouldn't read right. I did some research and found out that they did it to a lot of people. There was someone on FABO whose wife drove a newer Ram and it did it as well, the kid at the parts store had a duster with a slant six, we got talking and he said that he had a weird electrical problem with his tach, I asked if he was running E3's, he swapped them out and the problem went away.
As far as I'm concerned I wouldn't even put E3's in a lawnmower!