so today I got my o ring on my gas tank fixed and my filler neck repaced. My car drove fine for a while (2 HOURS ON SIDE STREETS STOP AND. GO) then now it has hesitation when accelerating it won't go over 40 miles an hour and sometimes goes as low as 5 miles an hour but now if I let the car stop and sit (turn it, off) it seems to accelerate to the 40 better again. It feels like its not getting enought gas. or something so then I changed the fuel filt and that did not fix the problem I took it back to the shop thinking they made a mistake but then they said it was my catalytic converter. but I don't see how that could go wrong at the same time as getting something fixed tell me what you think I'm going crazy here