renault megane 2002 1.6 16v - lotsa power with a fuel leak - snail renault

can anyone please tell me how my car is more powerful when the fuel line sprung a pin hole leak,it was literally going like a bat ot of hell. replaced the pipe and back to snail pace power. the car used to be powerful when bought it. it can't be electronics, if it is electrical, would the power disapear once fixed the pipe? same diameter pipe was fitted as we'll,ID and OD. any ideas?