Traced down a fail-to-start problem (thanks to info obtained from Stangnet.com) to a computer failure on my '92 GT, VIN 1FACP45E0NF114479, automatic trans. convertible. Replaced the failed unit, EEC-IV SF1-MA12A, A9P, E9ZF-12A650-CA with a unit salvaged from an '89 GT with automatic transmission, EEC-IV, SF1-MA12, A9P, E9ZF-12A650-C2A. The failed unit was equipped with an aftermarket ADS Super Chip performance module and what appears to be a stock Hypertech Power Module. The salvaged unit has no enhancements. The reason I believe the Hypertech Module to be stock is that it bears a '92 date. The car started immediately when the salvaged unit was installed and seems to run OK. However, before I finalize the deal with the salvage yard I would like to know if the two units are completely interchangeable. The slight differences in the model numbers indicates that there may be a difference between the two. Would also like to know what the ADS Superchip and the Hypertech Power module do for the engine's performance and should I consider installing similar enhancements on the replacement unit. ANY ADVICE IS GREATLY APPRECIATED.