I would say everything from a clogged fuel filter to a clogged air filter and many other things in between. Can you give a better description of perhaps when it doesn't accelerate well? Like when it's hot or cold, does outside air temp. play a role, etc. etc. Have you checked the timing? Tune-up recently? On and on........
Maybe if you can fill us in on what you have checked, replaced, and conditions when the acceleration is low we can help.
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