The Minifooger Boost (one of Moog's new 'board friendly stompboxes) offers two boost paths.
You can choose between up to 6dB of clean boost through a VCA (Voltage-Controlled Amplifier) signal path, or 12dB through a clipped OTA (Operational Transconductance Amplifier) path for more dirt. An extra 6dB is available for both paths if you use an expression pedal.
The VCA path offers quite a subtle boost, that won't give a massive jump in volume, but offers a nice tonal shift that enhances the sound and feel. The OTA path is nearer to a standard boost pedal, offering a touch of extra midrange and apparent compression.
This is an expression pedal that can undertake various tasks, depending on where you set the gain knob: from a full-range volume pedal, through swelling boost in and out in a musical fashion, or just hammering down for extra gain to drive your amp.