Haven't had all that much time to mess with cars lately but I have made some progress on tuning the ECU, and I got my used oil analysis back. On the short trips I've taken the car out, it's been getting around 14mpg :/
Despite the oil having 2000 miles on it and 10W-60 being notorious for shearing very quickly, my Castrol 10w-60 is still at 20.8 cSt at 100C! I'm going to start taping off the bottom portion of the oil cooler to block off more of it until I can get around to an oil change. I haven't been able to borrow a car lift, which I really want because the number of bolts and screws to remove on the bottom of the car is kind of silly. I think with only a small portion of the oil cooler exposed to fresh air, it'll hopefully increase oil temps to around 115C which will drop the viscosity considerably.
The ECU now runs much less rich in open loop, it goes into closed loop sooner, and I managed to get DFCO working, though it cuts out around 1800rpm in lower gears even though I want it to stay until 950rpm. I'm trying to figure that out, and also see if I managed to successfully lower the idle speed for engine on pulse and glide. Then hopefully increasing EGR and reducing some valve overlap will get me another 1 mpg on the freeway.