You can't really mod the Nano Muff - the parts are too tiny and PCB-mounted for any practical modifications.
And no, the regular Big Muffs are nothing like the Nano Muff. That's why it's not called a Big Muff.
The regular Big Muff pedals have much more gain, and don't have low end loss if you set the tone low. Heck, you'll get a bottom-end boost if you set the tone low!
When it comes to getting tons of volume and low end, opt for a Little Big Muff (thick, warm, and can ROAR!) or Russian/Sovtek Big Muff (somewhat harsher tones, a bit more popular since they've been around longer than the LBM).
But the tone control of a Big Muff has a variable mid cut. It's a good and bad thing, depending on how you're using it.
