My car has a hard time shifting gears it's an automatic vtec over 200,000 miles on 2000 Honda Civic

Starting up is fine but when I'm driving sometimes it feels extremely heavy have to push down on the gas petal for it to actually go over 20 mph and shift the second gear and others. I went to auto zone the diagnostic came back P1456 with a leak in the gas tank but I'm not sure if a sensor is messed up and need replacement or the timing belt or need a new transmission?

Asked by for the 2000 Honda Civic
seek complete diag and est b4 anything
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