Actually the XREAS and the Rear Air Suspension systems are totally seperate from each other.
You can get a 4Runner with either both systems or only the XREAS. All 4Runners that have the Rear Air Suspension also have the XREAS but not the other way around.
The issue you are describing relates to the Rear Air system.
My 4Runner only has the XREAS system so I can't offer any advice.