11.5 seems a lil low... is that highway or city driving? or a lil of both? you prob have 4.10 rear end which is whats killing your mpg... i would suggest a set of gauges first then a custom tuned chip like a Tony Wildman... also a DIY intake to let it breath better... that will give you a lil more mpg... let me know if you have any questions on these
-Raul