For Ford go to powerstroke.org and find the 6.4 sub forum. I don't know 6.4's (have a 6.0-no, and love it, after fixing it), but ask your specific question there and you'll get a concensus answer shortly. After deleting/studding/etc by 6.0 and having a 'mild' tune on, you can't wipe the smile from my face when half-assed getting on it. Tires don't like it as much, so now that the novelty has worn off I try and baby how its driven, except once in a while when passing someone.
