This weekend I got a CEL for the 2nd time since gutting the airbox. Both times it happened at WOT in the lower gears during heavy rain. I was concerned that the airbox might be taking in water, so I pulled it open to have a look. I was quite surprised to find that not only was the air filter wet, it was discolored at one end from taking in so much dirty water. When I removed the filter I saw that the bottom of the airbox had water spots, indicating that a significant amount of water had made it inside the airbox. What surprised me even more was seeing water spots on the underside of the airbox lid, indicating that water was definitely getting through the filter. This is on an otherwise stock MS6 with only the resonator removed from the bottom of the airbox and the diffuser plate removed from the inside of the airbox.
I ended up putting the diffuser plate back in the bottom of the airbox, but I'll have to wait for the next heavy rain to see if it actually helped. I'm still a bit shocked about just how much water seems to get into that area of the engine bay. As you can see in the last pic, even the inside of the "tuba" has some water spotting. After seeing this I'm curious as to how a CAI that puts the filter even further down in the wheel well can manage to stay dry.




I ended up putting the diffuser plate back in the bottom of the airbox, but I'll have to wait for the next heavy rain to see if it actually helped. I'm still a bit shocked about just how much water seems to get into that area of the engine bay. As you can see in the last pic, even the inside of the "tuba" has some water spotting. After seeing this I'm curious as to how a CAI that puts the filter even further down in the wheel well can manage to stay dry.