Hiccup at 6000
 

My 2000 model Boxster S has 160 000 km on the clock and is my daily driver. Its in fine overall condition but has a 'hiccup' at around 6 000 r/min for half second, then continues to rev smoothly. See attached dyno graph.
Any idea what could be the cause? The guy in the dyno shop thought it could be the fuel pump but the issues dont add up IMHO.
Inlet resonator maybe?
http://986forum.com/forums/uploads02...1579948391.jpg

My first thought was the resonance tube as well. However:

What I'd REALLY like to know, is if you held the throttle to keep it at 6k, does that "hiccup" still last a second? Or does power fall off at 6k and STAY off as long as you're at 6k?

Does that make sense?

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I had the same thought as Maytag but I'll try to ask it another way:

If you hold the engine at 6K rpm, does the engine continuously "hiccup"? If so, this could be caused by a fuel delivery problem (fuel pump, clogged fuel filter, dirty injectors, etc). It could also be an electrical problem, sensor problem, etc.

Or if you hold the engine at 6K rpm, does the engine hiccup for a second, recover, and then run fine at 6K rpm? If so, this is not likely a fuel delivery problem. This is something transient like the intake flap, variocam, etc.