I have a fairly weird but not knocking noise in the bottom end of my b20b. Full swap is a b20b with b16 head.. started maybe 3 weeks after swapping the engine. No idea what it is, still runs fine doesn’t get louder in the rpm starts going away after 22-2500 rpm. Only does it at idle, alternator is brand new and no other things are hooked up. Crank pulley looks to be ok but I haven’t pulled the engine to look around.. any ideas?