Intake Manifold flow valves

[FishinGuy1]

I have twin 175 2008 Suzukis. Port engine began running rough. Couldn't get it over 3000rpm. Pulled the plugs when I got back and 2 plug electrodes were bent closed. No marks on cylinder head. Regapped and engine runs fine. I have been told that the flow valves on the intake manifold loosen up and are sucked into the intake. As they are plastic, they are burned up and no evidence is left. Compression check on engine is OK and it runs fine. Should I pull the intake manifold? How serious is this?

[boats.net]

would be worth inspecting.

[FishinGuy1]

[IMG][IMG]F:\boat & fishing gear\intake manifold\6360web[/IMG][/IMG]
Opened up intake manifold & found 3 valves missing with parts of them in the manifold and the engine intake.