I don't understand the existence of 2 VE tables. I have read that both should generally match but why have 2?

Any comments would be great.

 

Primary-used when the maf is still active but only as a sanity check for the most part up to 4000 rpms and then maf takes over
Secondary-used when the maf fails but has less resolution than the primary

Why did GM use two? Who knows, redundancy at its finest.

Obviously they realized there was a flaw in that thinking and in 01 simply had the primary do the work in both maf & SD mode.