Which OBD2 tuner/reader should i use.

I know about hp tuners but I'm looking for a ob2 tuner/reader i can tune with software like mmc, efi live, and sct. I will be using this for diesels and some gas vehicles.

Unfortunately this isn't a simple question to answer since the options available will depend on the vehicles you want to tune and often you'll need more than one tuning solution. For Ford and GM vehicles both EFI Live and HP Tuners offer very good support. I'd suggest you spend some time on their respective websites and study the list of supported vehicles and see what is a better fit for you. Ultimately we intend to offer worked examples on both platforms anyway so either will work with our courses.