Figure this one out..... Im in my pit, fire up the engine....purrs like a kitty cat.... last and final call i head out to the the track, do my warm up lap and stop on my grid position - still purrs like a kitty cat.... I race my 7 laps and due to high speeds, wind factor and a lid covering my ears i only hear the muffled high revs of the engine...Im on my cool down lap, raise my left hand and exit. As i enter the main pits and idle in at about 3k i hear a loud consistant "clattering" sound from my engine - maybe top end, all the way as i back in my pit into my pit. very noticable....not so much knocking or pinging but definite "clattering sound......ANY IDEAS??