I have a 91 rx with a turbo engine swapped in. I had the engine rebuilt a few years ago. It has been parked as of late. I live in San Francisco and the emission laws are strict here. To the point I believe for the short term that I need to learn about some differences in ECUs and why some are priced different than others. It has been revealed to me that the one in the car is damaged. Secondly I'm desperately looking into learning more about the pre catalytic system and if there is an aftermarket equivalent that exists. Of course I'll take an original pre cat system if I'm blessed to find one. These are only to swap in for the machines. I totally intend to keep my down pipe.

 

in CA you need to have either a stock NA or stock turbo. if you do add aftermarket parts, they are supposed to be CARB approved, the HKS and Greddy stuff used to be.

part of the inspection is a visual, and you either need the original converters, or a CARB approved replacement.

for the ECU the US S5 Turbo is an N370, the JDM one is N374, which can work with a couple wires in the harness changed. the N350/N351 are for the NA.

 

California S5 T2 ECUs are pretty much unicorn status. I'd either try to find a shady smog shop or...yikes. Got any engine pics?