Someone installed a DOD FX80 compressor pedal straight into a C+ chassis?? Crazy.
I can help you identify any mods done to your IIC+. It's quite likely that more mods were done on the circuit boards inside your amp, besides the addition of the compressor and it's visible knobs.
I need to see some pics of the inside of the chassis. When he pops by, Boogiebabies will need to see them too. The chassis is really easy to remove, just unscrew the 4 bolts on the top of the amp, unplug the speaker, reverb and the fan (if you've got one) and slide it out the back.
Take photos of the whole chassis, and closeups of the circuit boards. Just be careful not to touch the leads on the big blue caps, they can shock you. You can discharge them by leaving your amp unplugged from the mains, but with the power and standby switches 'on' for around half an hour.
PM me when you're ready with the photos and we'll get them uploaded here.