techmanrtr

OK here it is a 1996 Tacoma.3.4 v6,5speed,runs like brand new engine .....sometimes it will start a very bad knocking sound on top end on right side just like an engine with bottom end problems......then it will stop for maybe 2-5mins or maybe for days.......it still runs like new when it starts making the knocking noise......have pulled valve covers and all shows to be find,seems to be on piston,been told it's carbon????......truck is like a brand new pickup .... down side it has 366k miles.....if it is carbon how can I break it done and get it out?????......thanks for any help.....