Popping with DI at end of signal chain

[David]

I don't know if this question is ultimately DI or DYI.  I'll let the mods decide and move it to the Lounge if necessary.  I'm using a Behringer GDI 21 ("poor man's Sansamp") at the end of my chain.  Last Sunday, I didn't use any of the simulations so it was just acting like an active DI and my rig sounded great.  Here's my problem.  For the last several months, the pedal preceding the DI has been a Mosfet Boost -- which I thought was screwed up because I heard a pop every time I hit the stomp switch.  Ultimately I scrapped it.

I recently completed a Muffer (I know, I'm a wimp...  but I was in a hurry and I have good luck with that circuit!) which I turned into a clean boost by leaving off the diodes and cap.  Even I can see from the schematic that it has caps and pulldown resistors on both the input and output -- so it shouldn't pop, should it?  Yup, I get popping with this booster too.  Hmmm...  I see a pattern.  Is it possible the GDI could be the culprit?  I know I could rule it out by swapping it out for a simple passive DI.  I'd just like to understand why this could be happening in the hopes that maybe I can prevent it.  I'm considering building a Condor to replace the GDI, and I'd sure hate to have that pop, too!

Anybody got any ideas?

[dualaud]

does it pop if you leave out the GDI?
does the GDI have insulated jacks?
did you lift the ground on the GDI?

[David]

does it pop if you leave out the GDI?
does the GDI have insulated jacks?
did you lift the ground on the GDI?

That's what I have yet to determine.
Yes.  The enclosure is plastic and the jacks are PCB mount.
I never lift grounds unless I absolutely have to.  I did not lift this one.