I had a Diablo inTune with a custom tune along with headers CAI 3" exhaust on my 2014 GMC Sierra 6.2. The difference was night and day from the stock truck. well worth the money IMO.

I currently have a 2016 Charger Scat Pack with the 392 Hemi. I have a custom tune using the Diablo Trinity tuner. I also have the 180* t-stat and just an axle back exhaust. The custom tune is from Hemifever tuning. They do All late model Mopars including the Rams. I gained 25hp and 25tq and you can Definitely feel it. The biggest difference is the removal of Torque Management in the motor and trans. The 180* stat doesn't add power but keeps the motor from pulling timing due to spark knock when it gets hot. The CAI adds about 5 hp and the ported 87mm throttle body adds 8-10 according to Hemifever. I plan on doing both of these mods as money allows.

The Diablo tuners work good after you get them fully updated. The update process can be a PITA but once it's done you won't have any issues.