It looks like I may need to replace my ECM. In looking on Ebay, I noticed that an ECM is paired with an immobilizer chip and a steering wheel lock/key. I have the following questions:

1. My RS does not have a remote control. Does this mean that it does not have an immobilizer chip?
2. If I have to have an immobilizer chip, can I just buy an ECM as long as I match it up with the existing immobilizer chip? If so, what number do I need off of the existing chip?
3. There were three Evo models built in 2005. Two with 5 speeds and one with a 6 speed. Is there a certain manufacturer number that I need to look for? For example, Ebay lists a "ECU IGNITION IMMOBILIZER ASSY EVO8 CT9A #312". The last number seems to vary.
4. I have a California car. I is there a certain manufacturer's number that I need to look for?

Thank you in advance for any help. Buying a replacement ECM is a lot more involved than my experience with other cars. I have had the car since it was new and it has never given me any problems until now.