I can tell you that we are *not* sporting a custom tune.
We're ~11.7:1 with a huge cam, 27 pound injectors at 55 psi and a ton of head work. We run a high altitude CPS and bored throttle body, other than that a stock renix system.
IIRC Dust Junkies Racing said that going to an aftermarket ecu with a custom tune was the single biggest gain they made to their race car, but you won't find a lot of non racers who do that.
I do have a JET ecu for Renix in the box of parts, but JET will not tell me what programming they change, and I'm not prepared to plug a bunch of unknowns into a $7000 motor.