there is a few plugs unprotected again water splash under the hood. even if there is no direct way to get them wet, a heavy rain+ speed can make water get to every place. buy some good high temperature electrical tape and finish the work. in most of the plugs the area were the cable is connecting to the plug is open, sometimes facing up.
I had a bad experience with a boost sensor under my hood because a heavy rain. I installed the sensor port facing up (my wrong). the water went down following gravity and enter the port. i burned the sensor, de gauge went crazy, i had to pullover under the rain,
so......
yes under heavy rain + 60-70 mph speed you can expect water were you should not expect it. you should double check for open electrical connections and fix it.

 

Make sure that you have checked for any loose connections on the intake piping, and any other vaccum hoses. Check for boost leaks. Also take note of what aftermarket parts or modifications you have installed that could be causing this condition.