Hi proinwv,
After a quick look at API 2000 7th ed, I see a small scope difference in the outbreathing section (>40 Celcius to >49 Celcius for air-equivalent flow conversion) and they added new equations for volatile liquids. They also changed the definition of what is vented during outbreathing from air to vapour/gases at actual pressure and temperature. In Annex D.9 there is a new table to guide the convertion of calculated flows from actual to normal/standard conditions. In the inbreathing section there is a new reduction factor equation for double wall tanks.
I saw some clarifications in certain parts of the standard but the main equations seem the same. Vent suppliers don't seem to have modifed their sizing software either.
I havent spent so much time to look for differences but I hope this helps.