I know the fuel injection system which is the KE Jetronic and you have
a M103 engine.What I don't know is if you have a pre-pump before your
fuel pump.If you do,the delivery rate should be about a pint in 12
seconds.A failing pre-pump causes stumbling and hesitation.
If no pre-pump,perhaps the plate on airflow sensor is binding.TG
suggestions of "secondary air could also be the culprit.Check the
vacumm hose that goes to system pressure regulator,and the rubber
boot that connects the airflow sensor to the intake.
Ultrasonic injector cleaning is about as much as new injectors and
IMHO,new is better!If you do a volume test,they should not differ from
one another more than 10%.Fuel pump should deliver 0.5 gpm if you do
not have a fuel injection pressure gauge.
You also stated you replaced ignition parts,did you by chance mix and
match the cap and rotor?Is there carbon tracking on the inside of
cap?Did you gap plugs accordingly?Are the plugs single electrode
platinum type?These suck in Bosch fuel injection systems and create
air-fuel errors.Sorry so many questions,but need a good idea so you
don't confuse a ignition problem with a fuel problem,plus it's cheaper
for you this way!!