Glad to hear you may have found the problem. It does seem unusual for water to get up under the seat to the ECM. Maybe the previous owner or shop used a pressure washer. 
Cheers, Richard
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09 America, Staintune Pipes, K&N, Breathe, Hagon Nitros, AI & O2 removed, tune 20184 (modified), MTX-L a/f gauge
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