Sounds like you should stop using the filter and filter oil.thanks for the o2 heads up. as to the k&n, i agree with you if a large amount of oil were to adhere to the MAF then it would screw things up. But if relatively small amounts of oil contaminated the MAF, that would be enough to affect the performance of the sensor without setting off the knock sensors from running the engine lean.
another way to diagnose this is a question. Do any of yall who have mpg drops have the k&n panels or is this just a universal thing?
Injector cleaner is a waste, its all in your head.Im not intending to put this up but just in addition. of course you need to run an injector cleaner to make it easier. On the other hand, you can use a scanner to figure out what's really behind those sensors. Got replaced two sensors and running the cleaner afterward.