From memory the Camry uses a different profile key than the MR2 and also the ignition is completely different. The immobiliser box for the Camry will be a separate box to the ECU, did you get this too, and the keys for it? I'm not 100% sure but I can check today at work but I didn't think that Toyota had a transponder blank in the same profile as the MR2, but a way to get around this would be to drill a hole in the side of the MR2 key, cut out the chip from the Camry and glue it in the MR2 key, then all you need to do for the ignition is attach the antenna coil which should be straight forward.
Might just be easier to change the ECU to an aftermarket one so you don't need the factory immobiliser :)