whilst they are interchangle and the car will start etc
some MEC chip types are not, you may find if you get the wrong MEC chip type, the car runs OK and idles etc but as soon as you drive it, it becomes mega sluggish and performs like ASS
i had this on my series 2 GTST with a remapped ECU, the remap was done to suit basic mods and i connected it up, took it for a spin and it ran like a bucket of crap
turns out the MEC chip type was wrong and i had to use a different MEC chip number. ask a remapper what the MEC chip type means, from memory the guy in sydney taso i think knows what it means