I recently put a SH-2 and a JB in my les paul and I've been loving it! I don't know if it's supposed to do this, because I've never payed attention to this in other guitars before, but I noticed that when I have a lot of gain on my amp and I switch pickups, I get a lot more hum on the neck or bridge position, but I get significantly less when I run both. In regards to hum, they're almost acting like single coils. I know the hum is definitely different from the single coil hum though, because I have a coil split wired to compare with. I don't think I have a ground/wiring problem, or do I?