I must have one of the Best Subie dealerships in my area! Before I started slightly- modifing my car(air intake,cat-back exhaust,rims&tires), their mechanic said if I ever had a problem...lets say..water sucked up into my motor...just to put the stock air-intake back on the car and they'd cover it! Even though they knew what was on the car(my Mods!),their mechanics would say "It was'nt modified" to the Subie Area Rep!
I think if you work with your dealership, they'll help you out. After all, you are giving them work and helping keep their jobs.