You're killing it with junk, soak in milk over night (if you want to save millk, can use 50/50 water-milk mix), pat dry, apply coarse sea salt and pepper to it (both preferably from a grinder), cook over very hot coals (I put mine about 5 inches from coals!) till medium rare (do NOT go more than med-rare, this is what screws deer meat up!) while basting with garlic butter occaisionally (just melted butter with garlic powder in it)--all you need is sea salt, pepper, butter & garlic powder--enjoy the great taste of backstraps!

BTW, make sure you get ALL the silver skin off, and get as much of the bigger chunks of fat off you can as well, this makes a huge difference.