That's interesting - I have chronic congestion. How much sugar did you eat before you quit? What did "quitting" mean to you? (Just no sweets/cakes/biscuits, or did you go more extreme - no chinese food!?)
I didn't think it was that much ... per day maybe couple of cookies, or a chocolate croissant, or hot chocolate. But almost always some kind of treat everyday. When I quit my nose cleared up in about 5 days, but the sinus headaches lasted another two weeks. That's when I knew something weird was going on.
If I have almost any dessert now I'll have a sinus headache the next day. I can get away with a teaspoon of honey in the morning and that's about it. Berries are ok but I'm still not sure about fruit (bananas are definitely not ok). But I can eat good bread three times a day and I'm fine.