Y6B Setup - Upper motors won't spin as fast as lower motors

Hello Fellas’,

I’m stuck at this problem and I’m not sure what to look for.

The problem is, that my upper motors never go above 1600 Pwm, while my bottom Motors are pretty much maxed at 1900’ ish.

I’m using all the same motors esc’s and props(3xCW&3xCCW same size). the weight is well balanced on the frame and vibeXYZ as well as the Clips is very smooth. Even the Yaw stability is OK. I just cant get the maximun aut of my upper set. Even though the yaw is stable it seems odd, that the upper motors wont be at least near the lower motors when I compare the RCOUT on the six esc Channels!?!? and yes the 6 ESC’s are calibrated.

I really need some good input here?

Thanks Fellas