I didn't catch this earlier. 2000PPM is at the speedometer cable. That is GM spec (2000PPM speedo cable) if running the right speedometer gears.
TBI ECM's and cruise are both looking for that 2000PPM (whether optical VSS, or DRAC output). I honestly doubt the speedometer being off by a modest percentage will matter much in terms of how it runs on TBI. There isn't a ton of refinement in the way those are programmed, certainly not like the OBD2 stuff.
Heck, the only reason I decided cruise cared about PPM, is that it's not supposed to let you enable it below ~25MPH. I accidentally hooked my cruise box up to the 4000PPM signal, and could then engage it at a much lower vehicle speed. But otherwise appeared to work correctly.
