Welcome. FYI, a bone-stock 335d will do a quarter-mile in 14.2. Launch is problematical; a LSD would help a lot.
Although 40 mpg is possible and sometimes attainable, I think you would be more likely to see mileage in the 34 mpg highway range (that's what I get here in Seattle going over the passes or down to Portland.) Lower speeds (under 60) definitely help with mileage.
I've been reading pretty much everything here in the last 3 years; I think there have only been 3-4 injector problems and most of them have been adaptation problems rather than failed injectors. But we're not in AK.