I have this annoying flat spot. The engine is a 2.0 16v (155hp). My two prime suspects are the ACAV breathers and the spark plugs. Can you suggest any more?
The engine is very sluggish up until 2500 rpm then lethargic to 3400. Then it takes off up until 4100. Its a real surge, then however the power delivery is very flat until 5500 when it goes bananas again.
It never used to do this it was a nice progressive powerful rush from 3400rpm till 6500 now there is a big flat bit.
I snapped the ACAV pipe when changing the spark plugs, a very noticeable difference with no surge at all anywhere in the rev range. I have glued it back on and the surge has returned at 3500 rpm but its flat soon after. If its not the plugs what else can it be?