Thanks for the ideas and comments. This is a project for me and my 17 yo kid since I let him have my '17 GSW. Told him it will run like a Golf R but $20k less in cost... he liked hearing that. He and I put it on lowering springs and B8 Bilsteins earlier this month. The kid is learning.
It looks like APR is the only off the shelf tune available. I don't want a generic tune, they're just a compromise but close enough. It's encouraging to hear that some folks are using Maestro with the IS38 in the 1.8. Maestro was my first choice, I am confident and competent in doing my own tuning as long i have something close to start with.
I have been reading the forums for quite awhile. I understand the main problem will be insufficient fueling at high boost levels. I do not expect to hit that threshold with a stock is38 since the R already has one.
I'm leaning hard towards Maestro, even though they officially don't support it. I'm going to need to need some help from the community if things hit a snag.