I have an MPX G2 and I love it. Even the envelope filter works for me, but I spent a long time working on it and ended up not using the standard envelope filter included in the box, but built my own. My big problem with the box is the fact that delays and reverbs don't spill over and mine has developed a very costly fault in the digitally controlled potentiometers which renders it unreliable. I've tried other boxes, but none them have worked out all that well and none of them sounded as good. There are some really great sounding effects in there! I love Lexicon reverb.
Is the issue you're having seem to randomly default to the place where the pots are set? If so, I had that issue too. I pulled it apart and cleaned the pots and it has been fine for the last couple of years. They seem super touchy for some reason. What settings did you use on the envelope filter?
Sadly, that's not the problem. The pots at issue are completely electronic and are digitally controlled analog pots mounted on the circuit board. So, sometimes it boots up, sometimes it doesn't and sometimes it just says "Digipot test failed."
Without being able to boot it up, I can't recall how I set up the EF. I'll see if I can get it going and work out what the patch was. The hard part was adjusting the sensitivity so it felt right. Once it was in the right place, I liked it a lot as it was a lot more consistent than my Mutron. Not as greasy sounding, but very good, nonetheless. Bear in mind that I am a bass player, so my model is more Bootsy than Jerry, but I'm sure it would work for guitar with some tweaking. Getting the downward sweep was a lot more challenging.