When it rains, atmospheric pressure is low, meaning there is a lower oxygen content in the air. You can probably figure out the rest.

 

Just a suggestion, Unplug the cam pos sensor and see if it has any water/corrosion in the connector. If it does, clean the water/corrosion out and then fill the connector with di-electric grease. I had a couple of cars come in with a bad connection to CMP sensor when I was working for Mitsu.

 

Ill give that a try, Cause when it happens to me, the car barely wants to drive.

 

Like everyone said, it's most likely water going in. It happen to my old car once.

 

+1 on water on plugs/coils combo.depending on where filter and intake are located water on/in mass would also be a nono.

 

Its water in the maf had same exact problem

 

I have an evo 7 hood with the vent and my cold air sits right there. And after rain last night it started an died out. Then I started it again and it ran...barely. But after it warmed up it ran fine. Just had a hard time every time I started it for a day after. And it threw a code p0121. Throddle position sensor. Wonder if that code will go away?:/