Kso, my buddy has a DA9 w/ a B16a swap from a JDM XSi and his current ecu is a stock 37820-PR3-003 410-XXXXXX AA ecu. And well my friend has a ecu that has written on the top in sharpie "89-91 SIR DOHC VTEC 1.6L" and it's code reads 37820-PR3-901 410-XXXXXX AB. My friend that drive the DA said he felt that it was smoother and his vtec cracked harder... Either way the "SIR" ecu we put it was said to have been stock also. According to what I pulled up from hondata they are the same ecu and there shouldn't be any difference.

Is there any difference like one being PR3-003 vs PR3-901(being in the 900's maybe makes it newer and the fuel mapping different?)

Or is there two different models of the EF8/9 in japan like SIR and ??? that hondata didn't include? or is it all the same thing and it's in our heads that the one with "sir" written in sharpie make it run a tad better?