How is gas mileage on Harley ultra?

with 408 miles on my new 2008 Ultra, a Power Command , Screaming Eagle Air cleaner and full exhaust ( rhineharts pipes and mufflers) my last tank got 33.187 miles per gallon. I'm hoping the mileage improves to that of my 2005 Ultra set up the same way pushing the mid 40's. I'm going to take the bike and have it put on a DYNO to have it all checked out for sure. I'm guessing the 96 CU IN engine will suck more gas and that's why the 6 gallon gas tank! Also I have been riding in 35 to 55 degree weather and some strong winds which also may account for the poor mileage right now.