an inherent problem with the circuits, and just as likely with the expression pedal. somebody on the CME forum mentioned that on the TRS jacks of most expression pedals, the output is transmitted on the ring while CME keyboards receive the output on the tip. so i think i'm gonna cross-wire a stereo cable to see if the pedal will work.
as for the breath controller.. sensitivity is dependent on the breath unit and not the keyboard. the jack merely supplies the needed 15V to power the unit and transmit the received signals to the midi translator. i hooked up my BC-3 and voila! it worked perfectly. but the 15V means the keyboard has to be powered via AC; USB power is insufficient(for breath control, as well as AFTERTOUCH). anyway, sensitivity on the breath unit can be adjusted using the "gain" knob and the air-leak valve on the mouth-piece.