Immobilizer Compatability from year to year

[TNT79Bronco]

Need those familiar with immobilizer compatibility between years. I have a 1997 Boxster, and the immobilizer is shot. Had ECU Repair Doctors do the diagnostics on the immobilizer and confirmed that the key fob and the immobilizer are damaged beyond repair. Since this is a "low budget" project Boxster, I am trying to stay somewhat economical in getting it running. Kind of a game..... The cost for a new key, immobilizer and programming of all the items is about $1,050, from ECU Doctors. Not a bad price, compared to what the dealerships charge, and for my 996, I would do it...now questions asked.

I wanted to know if anyone has knowledge of what year Boxster immobilizers/ECU units are compatible with my 1997. Here are the specifics of what came out of the car:

1. ECU - 99.0618.601.02 (Bosch 0 261 204 604)
2. Immobilizer 996.618.260.01 M535

I know that that it has to be an M535 and not a M531 Immobilizer. Learned that one the hard way.

I can find key, FOB, Immobilizer, and ECU for less than half that. (Yes...I know all the issues of replacement keys and VIN numbers and proving ownership)