My issue was/is injectors FWIW. I tried the same things as you, and same symptoms (idle, etc). Only difference is I'm stock motor/turbo, besides being side feed. My tuner and one of their techs took a look at the car, and related it to Power Enterprise's poorly built sidefeed injectors, and how their pulse width craps out over time. He loved PE up until about 4 years ago, and has had issues with them on Nissan's and Subaru's ever since (Nissan/Subaru are two of the main manufacturers out there that still used sidefeed injectors at the time).