Translating what you just wrote, it hesitates just as computer changes from closed loop (cold) mode to normal running mode. I'd first check the temperature sensor (computer reads it to know when to switch modes) Also, check the map sensor. it indirectly controls engine timing and fuel delivery. Another item to check is the manifold air temp sensor, which also influences fuel mixture. I don't recommend you run out and buy any of those items but you can test them with a digital volt/ohmeter using either haynes or chilton manual as a guide.