I have a 2019 and bought the 5 Star tune both because of the warranty, and also because the MPT tune wasn't out at that point. Honestly, the power gains were great, but the transmission shift points were atrocious. I worked with them, and they have great customer service, and really tried to help smooth out the shift points by sending me multiple revised tunes, but ultimately it really sucked and for me was un-drivable. The main issue was that 1st gear now has a ton of power, but it stalls out by skipping 2nd gear and jumped straight to 3rd where it would lurch forward again (just FYI, this skipping certain gears is how the factory shift pattern works in non-Sport mode on our trucks, not something that 5 Star decided to do). They did modify it to hit every gear, but the shifting was EXTREMELY rough, and uncomfortable to drive. I could never be certain how the transmission was going to shift at certain speed/RPM ranges..very inconsistent and unrefined.
I installed the MPT tune, and it is utter perfection compared to the 5 Star tune; butter smooth shifting and hits every gear. I am currently using the Tow version from MPT vs their normal performance tune, as I found the performance tune actually had too much power making the throttle too sensitive, and I was spinning my 37" tires too much when I wasn't trying to at stop lights (a good problem to have I guess!). But ultimately, I'd go MPT unless you're willing to put in a ton of time going back and forth with 5 Star on trying to clean up the shift patterns they have on their tune.
Just my experience and opinions, so take this for what it's worth!
