2003 Mercury 2.5l 200hp EFI Motor Loss of RPM at WOT ??

[Coxwain]

First and foremost- when addressing fuel lines, ALWAYS, ALWAYS perform ALL ITEMS at the same time:

-Line from tank to bulb
-Bulb
-Line from Bulb ALL THE WAY TO FUEL PUMP INSIDE COWLING
-Rebuild Pulse Fuel Pump
-Replace Fuel Filter and remove ANY debris in filter chamber.

Failure to do so will leave you chasing debris all over the system. IF debris passes the filter... it can become trapped in any of the following areas:

-VST Needle/seat (or passage
-Bottom of VST rear chamber
-Inlet screen to Low Pressure Pump
-Inlet Screen to High Pressure Pump
-Rails or Fuel Injectors

In your case... I would recommend you address all items NOT ALREADY ADDRESSED, exactly as above described.

I would ALSO recommend you check the BASICS:

-Compression Test
-Spark Test
-Fuel/Air Pressures (at idle, under acceleration, and 5/10/15 seconds after engine shutdown).

[Coxwain]

21-857005A 1 - Diaphragm Kit

is this the right part number for the pulse rebuild kit?

[EuropeanAM]

Yes. You will also require at least a 1/2 dozen 816311T Radius-Head Tie Wraps.