I've been having the same issues too.
My car threw the Bank 1 bank lean code and started to make this moaning noise. I cleaned and replaced the UIM and LIM with new gaskets last weekend and the sounds is still there. The CEL has not come back, but the noise is bad.
The moaning sounds like moosing, but very irregular and it's coming from the passenger side of the engine. Are there any hoses there? Also, it only happens between 1000 - 2250 rpms. The car seems to run fine except for the damn noise.
Any help would be great.
