Well, thats the problem. In Vemstune, you can't set a number lower than 30kPa at the low end. The top end is fine, I have it set at 350kPa and there is plenty of room there. I usually run about 300kPa manifold pressure when I get everything sorted and tuned. I would like to be able to tune the low pressure range a bit easier. I have the decel fuel cut set at 25kPa and I dip into that pretty regularly coasting, or even going downhill.
My map sensor seems configured right. It reads 81kPa with the engine off. Just about right for my altitude.