Incorrect prom ? In 846,only I was completely happy with noticeable improvement

[IANB]

After reading many different answers to the same question ,305 tbi to 350 including knock sensor,injectors .I initially just unplugged my 846 ecm and installed 747.I wasn't too happy with initial warm up ,and decided to put 747 asdz chip in my 846 and it worked great for about 2 weeks ,then I got the code 51with flashing ses. So I put the 846 back in and it ran horribly ,so back to 747,and now I cannot get ses light with either ecm ,yes I checked bulb , then I read it's not possible to run incorrect prom in ecm ,well for the 2 weeks it was running I was completely happy with noticeable improvement to engine ,so I'm left a bit confused

[dave w]

I've never tried mixing chips between different computers.

What I have noticed is when I look at a chip with the incorrect definition file.

For example:
ECM 1227747 is definition $42
ECM 1228746 is definition $61

Example of spark table using incorrect definition file.
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