Have seen NO evidence of it. Rumors, grumbling and talk radio are not evidence.
What do you need, a picture of him on a prayer rug?
The Won may not actually be a Muslim, but if not he is certainly a Muslim sympathizer.
What he is NOT, most assuredly, is a Christian.
He was asked once, during the 2008 campaign, who Jesus Christ was. His response was “a great teacher”, not “Son of God, sent to earth to atone for the sins of mankind” or anything even close to that.