It depends on if you have the 2 or 3 channel amp. If it sounds muddy, back off of the bass.
For a dirty channel, try this, put it in the modern setting, dial in you gain at about 2 o'clock treble at noon, mids at about 7:30, and the bass at about noon-1:00. If it sounds al ittle muddy, dail in the presence at around noon to 3 o'clock. That will give you a pretty radical sound. nice chunk for palm muting
Higher Presence settings can render the buzz! I keep mine lower (around 9:30), and season the high end with the Treble knob (around 1:00). The Presence control can also affect the Bass response! I keep my Bass around Noon. For a nasty, aggressive sound, some will lower the Treble, while increasing the Mids and Presence, totally heinous! I like my Mids pretty nuetral, say 10:30!
Try pushing the amp more....that is when the punchiness comes out. When I play me recto low, it is very unresponsive and almost as if lacking gain.
When playing low, having to keep the volume low, I also boost the recto with an OD.....I don't add any gain or drive, but it wakes it up! Maybe give that a try!