My oil pressure is fine when cold or at higher rpm's, but at warm idle it drops severely. I have a suspicion that it is the main bearings allowing the oil to pass through too easily, but I would love it if someone could tell me I'm wrong. The next time I pull this engine will be to replace it, but I would like to get more miles out of it. Could I get by with replacing the oil pump? Possibly with a high volume one?