This pop usually appear when switching off the amp before shutting down the lines. (That's the reason why it appears mostly when just pulling out the empeg without shutting down)

You could prevent from this pop by adding a capacitor to the amp-switch-line. It will load when amp is switched on and if the power is just taken away it will unload smoothly to give the amp time to recognize the lines are shut. Don't really know which size they should be - but they aren't that expensive (0.10 $ ?) so you could try several sizes.
Or just go to a car-audio spezialist and ask how to prevent from this pop. They should know (and maybe give you some better hints)

TeeMcBee
Got my Mk2! # 080000143