This is the first time with any of my cars I have had a noise like that. The clatter you hear to me sounds like poorly lubricated valves,being metal on metal contact.That's what I would suspect. Mine is like a grinding noise. The best way I can describe is is as if someone has a pepper grinder and is turning it to grind the pepper.

'95 CGL ZMTX - DOB: 8/94 - Daily Driver - 271k & counting - Ractive muffler,MSD ignition coil,KEM 8mm wires,Pre98 SE 7 spoke rims,KVR CF brake pads,Post98 sail panels,Sony Xplod HU,Pioneer 3-way 6x9's '89 Mazda B2200 - Under Construction