Are ECU's interchangeable?

I think the ECU is shot in my car, and I was wondering if anybody knows anything about replacing them. What I want to know is whether or not I have to replace the ECU with another one of the exact same type. Do the numbers have to be an identical match, or can certain numbers be interchanged for each other?

My car is a 1991 Talon TSi 2.0 Turbo FWD. The ECU I pulled from my car is numbered MD166260. There's another number under it that says E2T36574M. There's also another sticker on the side that says 6260 on it. Do I have to find another one with the same numbers, or is there another one that will work? If I have to be exact, anybody out there know anyone with a spare MD166260 that they're wanting to part with?

Thanks
Jon

I am not positive about exactly which ecu's you can put in your car, but I would suspect that any 1g turbo ecu will work for you. I know 2g ecus are interchangeable, otherwise people would not be able to put 95 ecus in their cars to run DSMlink.

Forgot to say that it's a 5-speed.

Would an ECU out of a 1990 Laser 2.0 Turbo FWD 5-speed work in my 1991 Talon TSi 2.0 Turbo FWD 5-speed? The number for the ECU from the Laser are MD128625, with E2T34474A written under that. Would that work in place of my MD166260, with E2T36574M written under it? The throttle bodies on the two cars are different. That means that at a minimum, the ISC Motor is different. TPS is probably different as well. What do you think? Will it work?

Thanks
Jon