different ECM's or ECM differences?

[Jason Weir]

almighty, Diacom lists 3 different configurations for the 91 4.3  (eng
code Z and year code M) they are as follows,

1991 GM/Chevy Truck 4.3 V6
1991 Truck Lt-Duty Emisn 4.3 V6
1991 GMC/Chevy Turbo Truck 4.3 V6

My question is in 91 did they offer something besides TBI.  If they
didn't what would be the difference in the ECMs.  The reason for this
question is that I use the first option (GM/Chevy Truck) but the second
option show alot more data, such as spark advance in degrees and knock
retard in degrees and 10 other things that my choice doesn't offer.  The
first option is the only one that will connect to my ECM.  I am
wondering if there is another 91 TBI ECM out there that has these added
outputs in the data stream.. maybe at 8192 instead of 160? Would it
still be a 747 or something else??? I can see the smoke coming now....
Jason

--
Jason Weir
88 Wrangler - 258 Chevy TBI
Fayetteville, North Carolina
http://home.att.net/~jweir
mailto:jweir at worldnet.att.net