The AGA Specifications include Part 1 "General Equations and Uncertainty Guidelines", dated 1990; Part 2 "Specification and Installation Requirements", dated 2000; Part 3 "Natural Gas Applications", dated 1992; and Part 4 "Background, Development, Implementation Procedure", dated 1992.
We based our AFC programming on the information in Part 4, particularly the Implementation Procedure; which means the 1992 edition is still the most current. The 1990 date of Part 1 means that the mathematics have not changed. Part 2 (the 2000 edition) is concerned with the physical lauout of the flow stream and measure ment methods, that is, how to install an orifice meter -- straight-pipe length requirements, how to control turbulence and cavitation, etc etc -- all of which is outside the scope of the flow computer.
Therefore, the AGA specifications for Flow Calcualations are based on the 1992 version of the specification that applies to our Flow Computers. There is no newer version of the applicable specification.