[Rocketstaples]

So I got a CEL at 17000 miles, and took the car to the dealership. The code was P0171. There was a leakage somewhere along the induction tube. They claimed that I had installed the aftermarket drop-in air filter incorrectly, and as a result, the induction tube came loose over time. They said that this problem is not covered under warranty, and charged $99 to fix it. I had installed that air filter almost a year ago, autocrossed with it last summer, and had it for over 10k miles, so I am definitely not satisfied with their explanation. Besides the air filter, everything is stock. Do you guys think that their reasoning is legitimate or should I try to take this up to Subaru and file a complaint? Thanks in advance.