Engine light comes run poorly in rain. Diagnostic test show nothing. on 2005 Hyundai Santa Fe

My vehicle was submerged in water the engine light came on. Replaced the charcoal something underneath. The vehicle engine light comes on when it rain. The car runs poorly slowing, dragging idle down. The entire air flow has been changed along with the EGR valve. The vehicle has been in the auto shop 6 + times. A problem is not showing up on a diagnostic test. Any suggestions to pass on to to teh mechanic. I take my vehicle to a Hyaundai dealership. Thanks.

FACT; You WILL be chasing that water ghost until you get rid of this vehicle!!....It has been H 2 0'ed...!