I have the Livewire, which I am somewhat disappointed in it because of multiple programming errors, wrong display units, etc, etc.
However, I towed my trailer last weekend, which weights 14,000 lbs. My truck is an '06 King Ranch 6.0 l stock engine. I used the standard programs (not custom because they are still not working), used the Jake brake and went up massive hills and back down them. The stock tunes on the 65HP mode with Jake worked awesome. I got a whopping 9 MPG on average and the Jake Brake worked awesome.
I also got back last night from Salmon fishing off the coast. My Aquasport 250 w/trailer weights 7000 lbs empty and I had 120 gallons of fuel on board. I averaged 12 mpg with the trailer up and down the local hills here. Still really good. My previous truck only got 7mpg average (Nissan Titan) pulling the same trailer.
I am mystified why the custom tunes don't work on my truck and it's a long story, but the tuner has pretty much been a thorn since I bought it, but the Jake brake feature and the added horse power is great. So, the truck has better economy, yes. The safety feature of the Jake is alot better and may have saved me from an accident this weekend because of road construction down an 8% grade. It's a love / hate thing with it now. I would have easily paid 3x the amount for a tuner with the same features that worked flawlessly and didn't have alot of issues. I have posted my complaints in other topics, so I won't go into a bunch of details.