Livernois has a tune for the naturally aspirated 3.5. I wouldn't expect a dramatic power increase since there are no turbos to work with but I suspect it would be noticeable. At the very least, it likely improves transmission behavior and throttle response. Tweaking the timing and AF/R should yield results. I assume your current MyCal would work on a 2018 and that their new device wouldn't be necessary. They could certainly answer that for you.