Incase anyone is interested this is an email response I received from Sebastian @Specialty Z (authorized Uprev tuner in CA). FYI they charge $500 for license, tuning and dyno time.
"Yes, there are some conflicting thoughts. AFR will change and that's about it. I tuned a G37 that didn't react to the speed limiter 
Uprev couldn't help me out or my customer on that one. Timing is tricky. We have access to the IGN maps but they don't seem to take. I changed the timing quite a bit to see if I could get some result and I could only get it too lose power
So as of right now we can do AFR, timing is up in the air (looks like a negative), VVEL is no go yet, rev limiter, and on a couple G37s the speed limiter wouldn't take. The 370s seemed to be fine. Tuning the AFR can make some decent, low, or no gains like you mentioned. On a G I did it gained a good amount of power considering. On a couple 370s we were able to get around 5-7 HP. The main goal would to at least make the AFR safe when modifying the car. Making it safer would be the goal. Power would be a icing on the cake. As you can tell, the bugs are still being worked out with the tuning software.
take care!"