Apparently it's Tube Screamer week. This is Run Off Groove's adaption of the classic overdrive to work around a CD4049UBE CMOS chip. More info, schematic and sound clip here. As you can see in the schematic, there's a resistor (RX) where different values will work for different guitar pickup types: 100k for single coils, 220k for humbuckers, 330-470k for hot humbuckers. I've included pads for a switch that will allow you to switch between 2 of the options. If you use the switch, remove the 100k resistor (which is RX) right by those pads from the board.