<FONT face="Comic Sans MS">Matt is correct. The stock tips are ceramic coated and any abrasive cleaner, (especially chrome polish, which typically is especially abrasive) will dull the tips rather than shine them.
My experience is just to clean them and live with the dullness, or you could do what I did, cut the welds that hold them on, get them chromed (cost me $50) and reweld back on. Mine look great now. </FONT f>