2000 Si with MSD external coil, rotor and cap, new wires and plugs (all iginition mods done 10K miles ago). Recently I washed engine bay (as have done dozens of times before) and car threw code of P1399, and misfires on all 4 cylinders. Problem only occurs after car warms up, otherwise during the first 4 - 5 minutes car runs normally. Any ideas? I'm thinking the coil, but the normal opperation at first has me confused. HELP!!

 

If the inside of the distributor is dry and MSD coil is fine, then I suggest that you replace the plugs wires. Look online for ways to bench test the coil. It's also possible that an auto parts store will do this free of charge.