K-Jet Duty Cycle Question

[Rato73]

I have seen a lot of discussion on the KE-Jet system, but I need some advice on the K-Jet duty cycle readings.

Car starts hard cold and idle is rough for approx. 15 seconds and then settles into a smooth 850rpm idle that gradually slows to 500rpm as it warms up. Acceleration is strong when car is cold but as it warms up, there is a stumble (miss) when pulling from a stop until 1200 rpm and then smooths out. Throttle response feels funny as there seems to be a lag between the throttle position and acceleration. Conversely, when backing off the throttle after acceleration, there is a noticible hard decelleration at a certain point like the throttle linkage is "unsticking"but it is free. Mileage is good around town but suffers on the hiway.

Connected duty cycle meter at pins 2 & 3 (X-11) on cold engine.
35% at cold start
30% after a couple of minutes when temp gauge starts moving
14%-23% at 2000rpm when warm, some missing noticed
07%-13% warm idle
00% key on, engine off

Am I correct in assuming that if the duty cycle's reading is decreasing that the engine is leaning out and is causing the warm drivability problems? The CD says that the duty cycle reading should be 40%-60%. Would adjusting the mixture screw to achieve 40%-60% duty cycle solve the problems? Any advice on where to go from here would be greatly appreciated.