2003 150 HPDI problems

[trcole]

I have A 2003 150 hpdi, it runs good over 4000 rpm's but under 4000, it cuts in & out on a cylinder.After 20 miles,running over 4000 rpms,I slow down just to dock & shut down for 20 min,when I restart it will have 2 plugs killed.(top on port side, middle on starboard side) I have changed all fuel filters,tested all fuel pumps,installed new plugs.I had a dealer try to read the ecm but he couldn't get any readings so he thinks ecm is gone.Any ideas where i go from here?

[boats.net]

Might test ignition components to rule them out, check voltage at engine when running.