Vacuum leak? Have you check for any of those? Might have some dry rotted "T" fittings around the S/C, LIM, Fuel Rails...I'd check those...you get some pretty craptastic MPG's with a vac leak...you can spray some carb cleaner around the engine bay while its idling...if the idle changes and it sucks in the carb cleaner...you might have found your issue![]()