I have a 98 F150 4.6 that I bought with a blown motor. I put an engine in, it runs great, except for a few issues. As the title states, I am throwing the Bank 1 and 2 Lean codes, along with a IAC circuit high code, and an intermittent o2 sensor code. Upon start, it starts and idle just fine, but once warmed up, it idles high, like 1300. It does not surge, just comes down to idle there. If I load it up with the clutch, it will "remember" its normal idle. But once i rev it up, it idles high again.

Also, after a long drive, once I stop, I notice a distinct burnt oil smell coming from the vents/engine bay. Before I put the new engine in, I put new gaskets everywhere but the head gaskets, just to keep that in mind. I lose about a quart of oil/3k miles. Part of me thinks intake manifold gaskets, but I put new ones on, so I also think that cannot be it.

 

Check the PCV elbow behind the intake.