I had a the same type of problem with my Tiico.  The van would hesitate and
kind of sputter at low RPM but once into the 2500 range was fine.  I did
retorque the knock sensor along with a lot of other checking of wiring
connections, grounds etc.  The van runs fine now.  The van would hesitate
and make a noise like it was pre igniting when it would hesitate.  Also some
times it would backfire through the throttle body.  Good luck

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