I'll share my experience with KEM. It wasn't good.
First card he sent bricked the minimax. H&S sent another, KEM hemmed and hawed, blamed H&S, but finally under pressure they sent another card.
They promised that they had made 500RWHP w/ a DPF on. I dyno'd it and the box stock H&S tunes were more powerful. No where even close to 500RWHP.
The tranny shifting was horrible. I thought it was going to break the truck. At one point it didn't engage and I hit the throttle, then BAM. Thought sure it hurt the truck. I babied it home and got the tunes off.
They promised they made 22mpg. What they don't say is that they hide the fact that this was on a 2wd, on dead flat road @50mph.
It freaked out the lie-o-meter. Thing would read 22mpg, but a hand calc showed more like 13mpg. Yes, that's worse than the box H&S tunes.
Terrible turbo oscillation under light throttle use / cruise control. Did the wastegate adjustment KEM said it needed, made no difference.
Guy was rude as hell to me when I wanted help and he refused to fix the software.
NO RETURNS! Even when it's clearly defective.
Your experience may be different, but I won't touch KEM again. To be honest, these tuners that get every last grunt of HP out of a truck is IMHO a mistake. Running everything on the ragged edge is bound to have longevity issues. Truck has a ton of power now, between that and my right foot it's very hard on tires as is. I've got 35,000 miles on a delete/tune without a single hiccup. I'll stick to my box H&S tunes for now.