[sausagehacker]

I have a standalone and it has improved my gas mileage noticeably, because the AFM is out of the way and I can lean out the car to ~16:1 on the highway and get 34 mpg at sea level. The stock DME uses batch fire...which at idle, succumbs to intake pulse reversion and fuel gets splashed into adjacent cylinders. With semi-sequential or full sequential fueling via standalone, idle is dramatically improved and you actually use less gas at idle to achieve a solid AFR (because intake pulse reversion doesn't affect it as much, hence you don't need to compensate by adding more fuel). Therefore a well tuned standalone can easily get an even better emissions score at idle.

In TX I got this car inspected with the MS unit literally sitting on the passenger seat and the ignition coils in plain view in the engine bay. I know it's not CA but the spirit of the law is to enforce federal EPA regulations and to crack down on people who modify their engines in a way that leads to more hydrocarbons and NOx in the air. A standalone has nothing to hide unless it was tuned poorly.

Anyone who relies on their CEL to keep their car running shouldn't be considering a standalone, that should be obvious.