75 hp E-Tec drops back to idle speed

[Troutdoc]

2004 75 hp evinrude e-tec with less thn 100 hours.
Cranks, idles, and runs fine up to appx 4500-4800 rpm. Engine then drops back to idle speed.If I bring the throttle lever back to idle, or neutral, then the motor will acccelerate back up to 4500-4800.

My dealer says I will have to leave the boat with him for a minimum of 4 weeks, maybe longer.
Help.

[boats.net]

Sounds like a fuel problem, need to test fuel pressure and check all fuel filters. Check all fuel hoses and connections.