I note that these are your first posts so I welcome you to ThisIsMS, pbcb8835 and offroad44.
Pineapple contains a substance called bromelain, which reduces inflammation and congestion. Ibuprofen is an anti-inflammatory, I believe; however, it is my understanding that Tylenol (acetaminophen) does not reduce inflammation. Perhaps it is bromelain's and ibuprofen's effect on inflammation that is reducing your side effects with Avonex.
My hypothesis: excess insulin (hyperinsulinemia) plays a major role in MS, as developed in my initial post: http://www.thisisms.com/forum/general-discussion-f1/topic1878.html "Insulin – Could This Be the Key?"