just an FYI (and im not saying anything against you, just making a point...)... to the ear is not an accurate assesment of intensity. people who have sat in 160+ vehicles sit in my car and swear up and down that i am playing at 155+, some have even said that it seems very close to 160. but as far as building pressure for the mic, it doesent do it... im only doing a 148.8 legal.
pressure gradients in a vehicle can be so widespread as well, could be doing 160 at the dash, but 140 elsewhere in the cabin. for a daily driver (which was what i built my truck for), the mic score shouldnt matter, if its loud, its loud. but if you are going to claim a number on the mic, dont try to back it up with "it sounds that loud"