Uneven Throttle position at midrange driving twin 700csi with NXT drives
 

The port throttle is at 52%, While the starboard throttle is at 38% when running at 3000 RPM both engines.
The compression is in normal range in all cylinders, and there is spark to every cylinder.
The throttle levers stay approximately 1/2 inch apart, and the speed at the top end suffers.
Any advise?:thankyouthankyou