I haven't even thought of MMS in a nasal rinse. The putrid odor from the concoction would be enough to cause all sorts of nasal problems - regardless how much you dilute it.
What I have found to be very effective is the addition of Tea Tree oil - about 3 drops to a pint of saline water (1 teaspoon of sea salt and 1/2 teaspoon of soda to a half pint of body temperature water). You may wish to start with just one drop and work up to what seems best for you. I'm at about 6 or 7 drops and this in a Neti pot keeps my sinus clear for hours.
Tea Tree oil kills infections and it also provides an aromatic nasal clearing ability at the same time.