Interesting. Have you cleaned or replaced your injectors?
I got into the low thirties MPG in my 10v 90q driving from Minnesota to Pennsylvania. I did about the speed limit the whole way. Shortly after this trip I replaced the fuel injectors with Bosch OEM ones which had the effect of lowering my average MPG but increasing the engines performance considerably! So I think the restricted injectors actually saved fuel. I still average far better MPG than the federal estimate suggests. 16 city 22 highway is a downright insult for the 10v 90q. You'd literally have to drive everywhere with your foot to the floor to achieve that! I get maybe 18-19 mpg with a lead foot round town and at least mid 20's on the highway.