My 94 with a D15B7 does this too, right around 4000 rpm there's a noticeable increase in power and even the intake sound changes a bit. My brother's old 93 CX (canadian) hatch with the D15B7 also did this. I remember reading something a few years ago in popular science or some mag like it that said that most all multivalve engines like ours really need to be revved above 3500 rpm to get any real power, and that was due to something about intake velocity and better cylinder filling at those engine speeds.

 

its called a tune up needed and adj timing, do you have a intake? the noise you hear is called valve lash from high rpms

 

Timing is spot on and tuneup was done in February. I've just got the stock intake with the silencer horn thing removed.

 

glad it's not only mine doing it......thanks 4 replys

 

My 95' D15B7 does the exact same thing around the 4000 rpm area, runs like a clock.