So, I figured I would update from my perspective now since it's be a little while...
As I said previously, the dealer was convinced that the K&Ns where over oiled which was causing issues with one or both of the MAFs. I noticed that cleaning the MAFs seemed to help for a few weeks but eventually it would go back to consistent losses in power or limp mode.
As of this last winter, things got really bad. My car started to regularly go into limp mode and threw codes far more frequently than before. Cleaning the MAFs had little to no effect on the situation and sometimes restarting after the oil temps raised the needle just off the floor seemed to help for a single trip (until the car was parked for the day for instance). Sometimes after this cycle, the CEL would come up and the same codes that were previously pre-failed would now be failed.
So I started to systematically replace parts that the dealer mentioned and get it to a state where either it would fix the situation or prove that the problem was not what the dealer was claiming it to be. I started by removing the K&Ns and making sure everything in the intake was fresh and clean, then replacing them with brand new stock air filters. Then I replace the driver's side MAF. The car ran good for a single trip then went to limp mode. I considered moving the MAF to the passenger's side and putting the other in but ended up saying screw it and just ordered another replacement MAF. (This way, both are replaced and the dealer has no leg to stand on anymore.) Again, after replacing the second MAF the performance was good. In fact, the performance was GREAT, way better than it had been in a while. Drove that way for a few trips then BAM, something started to feel off... Ran the codes and sure enough, pre-failed P0101 and P010B. No oiled air filters, two brand new MAFs; this problem is not due to fault sensors and/or caused by the air filters, I'm now convinced.
I have an extended warranty for my Z so I will be bringing it into the shop soon (probably when I go to get my winter's rotated off) and raising a small but rather steamy level of hell! I'm thinking about pointing them in the direction of the throttle bodies and telling them to clean and handle the relearn process.
I'll update again once this is done. Thanks for all of the information everyone has shared thus far, it is really helpful!
