I have a 350 fuel inj engine in an '88 truck that started using oil really bad (quart every 100mi). Only smokes a little upon startup, but it always did that. It has 123Kmiles and didn't consume oil hardly at all until recently. I notice the idle is also very high, around 1200rpm. And the oil gets dark very quick after it was changed. PCV valve is clear. I'm wondering if possibly the intake manifold gasket could have ruptured internally causing crankcase oil to be sucked into the intake manifold and burned?? The engine runs fine and has plenty of power, just uses oil.