I have inherited a friends project car. As the title states its a b20b b18b heads, Crower stage 2 cams, skunk2 throttle body and intake manifold. The cat has been gutted with a greddy cat back exhaust. Gsr exhaust manifold and an eBay ecu chipped with knowing what the mods were. The problem is a rattle from 3500-4000 rpm. All heat shields have been removed. It almost sounds like header or valve train to me. Is it possible that a crank bearing could cause this? Kind of lost on this one not sure what it would be for sure.