My NA-T arrangement retains the OEM ecu, fully hooked up with exception of the coil ignitors and injectors - leaving fuel/spark control to a programmable ecu.
To pass emissions, I see two options:
1. Clear all codes, swap to stock injectors, and give fuel/spark control back to the OEM ecu, do some light load driving to pass all the OBD-II monitors and show emission readiness. I'd go in for my inspection, then go back home and swap back to the big injectors and give fuel/spark control back to my programmable ecu.
The injectors in my car are incapable of delivering the tiny amount of fuel required for a 14.7:1 AFR mixture at idle and very light loads, which would be required to prevent the toyota ecu from detecting an overly-rich condition. I also do not have an operating switching O2 sensor in my setup, which would be required for fast-closed loop control that dithers back and forth from rich to lean, right around 14.7 all the time.
2. By upgrading injectors to newer, fancier units with faster response and better low-fueling characteristics - and adding a switching O2 sensor, I believe I'd be able to satisfy my OEM toyota ECU "watchdog" - fooling it into thinking it was, itself, doing a fine job of fueling the engine.
...all of this obviously assumes you have a good working catalyst and all your OEM pre/post O2 sensors in place...
Last edited by Hodgdon Extreme; 02-19-2019 at 02:31 PM.