dan, when rob m and i were working on the 91 3.0 v6 cal we experienced the same issue and were able to resolve it by commenting out some very specific code in that cal. when i get back home from vacation i'll see if the v3 code has it commented out also.
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couldn't wait. i looked at the v3 code and this line "jsr EmmissionMaintenanceRemider1_MM" is NOT commented out where that line in the v4 code is. you could search for that line in the v3 .asm file and put a semicolon in from of it like this ";jsr EmmissionMaintenanceRemider1_MM". then recompile your template with mptune and see if that helps. there are a couple more routines that may affect it but i need to compare the v6 cal to the v3 code to confirm what all needs to be done.