Falha de aceleração no Fiesta Fiesta XR2i

Hello, it happens to me that when I accelerate suddenly I start to fail and head, I do not stop or anything, but it fails as if it worked in 3 cylinders, but in the morning when I turn it on it works well, there it starts to fail and out there, a year ago I had to lower the gas tank because it had some stones as if they were crystallized naphthaline Tremendous, I remain well, but out there this fault comes, I don't know if it will have remains inside and Quando eu exijo, o duto é pego ou que, alguns dias atrás, tive que mudar o regulador de tensão desde que iniciei o alternador 22 volts e queime várias coisas no carro, se alguém puder me dizer por onde começar a verificar se é muito apreciado ...