Red hot Remus pipe

[Big Lad]

Just got back from Le Mans. One of the blokes behind me signalled me to pull over. My remus pipe was glowing red hot inside the pipe and the can had apparently been spitting out sparks. When it cooled down I could see small shiny metal lumps around the end of the pipe, looked like tiny iron filings. The obvious question, is this normal ?. Our riding had been fast, but surely not enough to cause this. Enging temp was 5 bars all the time and no loss of power etc.