engine loses power around 4000rpm

hi there all, i was wondering if anybody could help me please,my 1992 300zx tt manual is losing power at around 4000 rpm as you are acelerating to that point all is fine then it feels as though you have hit the brakes as you lose power,the motor does not stall.any help would be appreciated thankyou..

 

Limp mode?

Do an ECU self diagnostic to start with... it's in the tech section.

 

thanks

thankyou very much. :YD