TAR+ Vintage Metal Distortion ZIMcard
is a tweaked version of the classic distortion circuitry used in Distortion +, Rat, and other distortion pedals. It produces a nice 70s/80s style crunch with plenty of gain and output volume. Think Judas Priest, Scorpions, Maiden, Dio, Metallica. T+ digs deep into old school heavy metal sound.
T+ works well with BB by setting up BB as a post-distortion volume boost. T+ has plenty of gain on it's own, so ZIM's other channel can be used to boost leads.
You can set it up with T+ in A, and BB in B. A alone will be your basic distortion tone and switch in B for a volume boost and a change in voicing.
Or, try it with T+ in B and BB in A and swap order. Run A after B by going into B and patching the output of B into the input of A, and output of A to amp. This way, you can use B for your distortion tone with a voicing, and kick in A for a straight volume boost.