low power above 4k rpm

[Ray Kawski]

> On Jan 22, 2018, at 11:40, David Pertuz <d.pertuz at gmail.com> wrote:
> 
> I noticed yesterday that it still more or less falls on its face above about 4000rpm. It's not a hard ignition or fuel cut, but it stutters and power sort of plateaus.

Sounds like MAF.  Check MAF voltage or for stupid lazy test unhook MAF sensor connector and drive it and see if it any different.   If it’s not different then MAF. 

RK