the custom isn't as scoped in the mids.
heres what dimarzio says about it
the blaze custom model has a very distinct "clean overdrive" sound. The blaze custom bridge was built for 7 strin players who prefer a hotter
bridge pickup with more mid-range. Because more power is focused in the middle of the guitars range, the blaze custom bridge will overdrive an amp more easlily and the sound will be fatter. We still didn't want to make the seventh string muddy so we used our dual-resonance desinge to add some crispness to the low end. You'll get more attack and hottoer harmonic overtones too.
its specs are .
lows 7.0
mid 7.0
highs 6.0
output 410 mv
dc resistance of 16k
compared to the normal blaze
highs 6.0
mid 4.5
lows 7.5
output of 380 mv
dc resistance of 20.75