Not trying to lecture you on smog rules James, I know you know them well, just trying to answer the question. The answer seems to be based on weight and california or federal build (but then again I have been wrong before) ASDU comes back as a Federal prom. I also think that about then ( 91 gmt-400 trucks) is when they started doing away with smog pumps and just using diverter valves.

115 does seem really rich at idle. This is going in your Burb right? What size injectors are you running, and how much have you tweeked the prom?