no, p setting does not affect MF at all. It affects the nopdrop chance, or the chance that any item has to drop at all. The only thing that affects rune drops with /p settings is for the countess. I think its because she drops like a boss, and she will override her special rune drops with an item at higher /p setting.
That's why light zon's run cows on /p7 and if it wasn't too slow, a barb would do travi on /p7 as well.