On gas engines, the experience I had with them on my previous vehicles was that I saw the improvements on the transmission performance more than the engine itself.
UNTIL you start doing things like adding bigger injectors, a supercharger, bigger MAF, etc., that's where something like an SCT Xcalibrator that you can custom tunes starts to shine.
Yeah, you can up the speed limiter, change shift points and firmness, select economy, tow or performance settings, but I never saw "white knuckle" increases in performance.
The transmission performance was the most noticealbe improvement.