I have posted this point before but here it is again.
This question comes up/came up often with the Duramax. My conversation with one of the designers/owners of a company that does high end tunes for that engine told me that the engineers for these vehicles design them so that you get the most out of them with the least possibility of doing damage to the engine. Even a moderate tune takes some of the long term life from an engine. It does some damage, however slight. You may gain a few horsepower and torque. Most will tell you that the fuel mileage is a myth but the overall gain will shorten the life of the engine.
In the case of the Duramax, even though the Allison is bullet proof, they always suggested beefing the transmission if you were going for major HP gains.
So it is buyer beware.
2018 Jayco Greyhawk 29MVP
2019 Jeep Sahara Unlimited
2011 Cyclone 3010 Toy Hauler- Sold
2014 Chevy Silverado Duramax LML -Sold