There's an idea the INTP mafia could provide services in terms of transport and communications, the idea being the more people a message goes through the more likely the investigators are to loose track of it, a giant game of Chinese whispers in various codes with a red herring or two to really fuck things up.
Or here's another idea, we help the police, so we hack/snoop and get in on things and sell out various unprofessional criminals and then run a protection racket on professional crime organizations while simultaneously offering them various services like the communications idea I just mentioned, basically we screw everybody

The trick would be finding a balance between being criminals ourselves and being on-side with the police, at least having them think we are.