It rained hard and I lost a lot of power...

[DieselHead]

Hi,
It rained steadily yesterday, and hard at times, which somehow caused my car to lose a lot of power. It doesn't maintain speeds that well anymore, and it takes a lot longer for my turbo to spool up (I have a gauge that tells me as such) and the acceleration is definitely not what it used to be. What the heck could be my problem? I know it's directly related to the rain because this has happened once before when it was raining hard. The last time it happened, I changed both the clear and the spin-on filters and it fixed my problem. Do I have a leak or something somewhere? I should mention that I have an exposed air filter, but I took a look at it and it did not get wet (or seem to get wet). Thanks for the help! So far I'm theory-less.

Alex