There are 3.5 bar MAP sensors as well as 5 bar MAP sensors. AEM has them. They are pricey tho. And a few PSI above 30 wont make too much a difference as far as alky amount.
If you have to run past 30.. you may want to look at air flow mods like better heads/cam/exhuast/displacement to make more power at less boost. I have seen a 109 block run 9.50 in the low 20's for boost.