Copy and paste your original post into an email; add some detail on how much and how often you plan on towing, and send it to some injector shops. I did all the research a few years ago and ended up calling around and taking a recommendation from the shop that was happy to spend 10 minutes on the phone explaining things. That was DFI. If you get the same recommendation from multiple shops, its probably a good idea, and how thorough their answers are willl tell you who wants the business.