i have a 99 forester with the single cam 2.5. I am taking it down for maintenance the head gaskets are bad(no coolant in the oil though) and i noticed an odd noise idle is fine, full throttle is fine, but above 1800 especially 2500 there is a rattle just maintaining rpms. it does it on the highway too. anyone on here think its rod knock, or anything else for that matter? it sounds like a rattle.