Scan the codes first to give you a base from where to start. Then see if that will give you an idea. Two major things that control fuel as the thing runs are, MAP sensor and O2 sensor. Tps is not as sensitive and since you didn't adjust that during the swap, I wouldn't be concerned. Besides it doesn't make the fuel rich in this condition. A poor ground to the block can make the system go into closed loop which can cause this thing to belch fuel emissions. Check the codes first and see what it says. DId you use actual 305 computer for this? or keep the 350 computer and change chips? The two computers are flashed for each application and will cause the thing the do goofy things by rechipping it alone.