Paseo sputtering?

This 92 paseo with the new engine (car is mechannically sound) I just found out sputters when you put your foot on the gas. After that its fine. A regular mechainc thought all it needed was a fuel filter but that is not the case. He cant find the problem so he told the guy to take it to a toyota shop. SO im wanting to know what the problem could be before I buy the car and shell out more money.

Its only when you put your foot on the gas hard to go. Like when you gun it or when your needng to give it gas cause your at a stop sign on a hill and it does it. Driving normally its fine. NEED HELP QUICK!!

Have you checked your air filter? What about your fuel filter? Or even a small amount of water in the gas will do that.