Regarding the sloped vs flat IFR table conversation, it is really quite pointless.. (well, at least we could say we are running in circles)
97-03 GTPs.. Same fuel setup. 97s (all I have seen) have stock flat IFR tables from GM. 98-03, all have the same stock sloped table.
So, same fueling parts, different style of stock table data. There has to be another factor in the tuning that accounts for it.