I have started to have a problem I need some help with.  Check the forums and could find no other mention of a similar problem.  First of a disclaimer,  I am running Win 8.1.

 

So here goes.  When I take off, with a moderate payload and fuel,  after climbing to about 5 thousand, I can't get my speed to increase above 200- to 220 or so, even with the AT and AP off and the throttles maxed out. Both Engine instruments indicate  normal,  But I can barely climb, if I increase to above 500 fpm, I start losing speed.  It feels about like a DC6.  When the program was first loaded, worked fine.  It started after I also had the famous losing controls problem, which I resolved with a registered copy of FSUIP, and disabling the Win 8 pwr save feature to the USB ports.   But that said, controls seem to be working great.  And yes, in flight I checked, no gear down, no spoilers up, nothing seem amiss, just no power.  

 

Appreciate all works of wisdom

 

 

What kind of throttles are you using?  Are you getting >100% N1?

I had problems with my throttles maxing out at 80% and had the same issue.