Compression RATIO is a mechanical calculation that is not influenced by intake pressure/boost.
Without knowing a lot of detail about the 2.2 engine/head/intake/engine cooling/intercooling parameters and how you're going to use it, you won't get any reliable answers of how much to decrease CR for a given amount of boost.
A really WAG would be to go with a 9.0 CR and limit boost to 5 psi. That would give you good low-boost performance and a nice increase under max boost.
Or........going the other way.... a 8.0 CR and 8-10 psi, which would be a bit sluggish on the low end, but a real push under max boost.
Those are conservative suggestions, since I have no idea what your expertiese is and how stout your engine will be built.