I use System 96 glass, but I rarely get devit. There are a couple of colors I’ve had problems with – dark purple transparents and a cream-colored opal. I think it’s just the tendency of the glass, not the kiln.
If you use ThinFire, try using kilnwash. I hear many anecdotal reports of ThinFIre causing devit on Bullseye. Ironic (and questionable IMO), since Bullseye makes both .
Jester’s Baubles Fused Glass Designs