Swp, Whats your diet like?
Also how you feel about HIIT?
My diet is, make myself eat disgusting fruit and vegetables and lean protein, and don't get wasted every night, and Nutella is not a food group.
HIIT is great for building both speed and endurance, as I'm sure you know, but I prefer incorporating speed intervals toward the end of a run (typically 3-5 miles, longer if I don't have some sort of class that evening), and then only about .5 more than what I was going at, ie 6.5-7.0 or 7.2. (I am not fast).