Revalver MKIII.......yes another one!

You need to turn down the gain to like 5 or 6 and turn up the input voltage to like 3 volts (it's in the tweak menu in the input/output section). The input voltage compensates for the volume from your pickups, the default value is set for singlecoils I think, and will give you the same amount of gain singlecoils would give you on a real amp.