Partial throttle problems

["Chris C" <petleech@xxxx>]

We have a 1983 DMC with 84k miles on it, which we have refurbished. 
Since we started the engine, upon deceleration or light throttle the 
engine bucks and jerks. We have replaced fuel pump, filter, 
accumulator, injectors, distributor cap and rotor, ht leads, 
plugs,oxygen sensor, and injector seals. A Volvo specialist has set 
the mixture and the timing is at the prescribed 13 degrees BTDC. We 
have tried everything we know possible, and have checked and fixed 
every vacuum leak. The car accelerates smoothly, all 6 injectors 
deliver exactly the same amount of fuel, the frequency valve is 
operating, we have set the throttle switches correctly, the vacuum 
advance on the distributor is not sticking. Any ideas on what could 
be causing this? Nothing we have done has had any effect. We notice 
even with new injectors at low flow, the pattern is not a perfect 
cone on every one. Could it be that the new injectors are bad, and we 
are not getting perfect atomization at low flow?