11" seems low with that cam at 900 rpm. I'd square up the transfer slots and use the IM screws to give you max vacuum while adjusting the idle speed screws after each IM adjustment. If a IM adjustment raises rpm, the engine wants it.
When I get the trans back in I will be checking vacuum at idle and cruise and go from there as suggested. Woulda had it done this weekend but UPS delayed shipping again.