Leigh and I guessed that all the card tells the PGM is;

a; it's serial number (so it knows it's not being nicked)
b; what card it is, i.e. the PGMIV "knows" all the ign curves, what display to use etc.

This little hypothesis is based on the fact you can remove the card if you run the HRC loom and the bike still works. In fact if you turn it off (with the kill switch) for a couple of seconds then back on it'll start again, nothing needed is held on the card, once it's told the PGM what to do it's seemingly redundant, it's just a switch.

I doubt a stock PGMIV can run any other maps than the available cards. Even the 525 which was an HRC special might be for a totally different (internally) PGM.
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