Which ECU????

Ok, here's the deal. I've got a '92 Eclipse GSX. It ran great for the 4 years that I drove it and then one day just DIED! After reading post after post after post on several different sites I came to the conclusion that it was worth the effort to pull the ECU and check it out. Took the cover off and my question was answered. It was shot, the acid from the caps had actually eaten through whatever was holding a few of the really small resistors on the board. To put it bluntly.....the ECU is fried.
Here is where it gets tricky. I bought the car from a 55 yr old woman who had just had the ECU replaced. ( That was like 5 yrs ago ). The reason she sold it was because after they replaced it, the car didn't have the same get up and go that it did BEFORE they replaced it. The car was still fast.....just not what it had been. I had driven the car before the ECU change and she's right...BIG difference. In fact, I was the one who showed her what happens when the boost guage hits 12. She about wet herself.Now the ECU that is in the car came from a salvage yard. My questions are these.....
1) How do I know that the ECU in the car was the right one?
2) How do I find out which ECU needs to be there?
3) Where do I find a "good" ECU that isn't going to cost me more than what I paid for the car?

BTW, the P/N on this ECU is MD166262 ( Is that the right ECU??? )
The car is a 2.0 Ltr, DOHC,Turbo,AWD,5-Speed car if that helps anyone.

Thanks!