Adding a gain control to an Acapulco Gold

[Tuxedo3]

Hey guys, I'm looking for some resources on how to add a gain knob to an Acapulco Gold circuit. I had some boards fabbed and they work perfectly other than the gain control. It only works with that turned all the way up. It's a 1MC pot and pin 3 is the input, pin 2 is the output, and pin 1 is grounded. If the control isn't totally dimed I get crazy feedback and no guitar signal, but if I turn it all the way up it works great, just a bit too gainy for my application. Anyone have ideas? It's setup like this http://pedalparts.co.uk/docs/SunnTAMZ.pdf schematic.