yelocorado

My car runs fine untill I am driving it about 20-30 minutes. After that, I give it gas and it starts to sputter. I give it more gas and it takes off pretty good, but if I keep it at a constant RPM, It will sputter again. I thought it was the o2 sensor, so I unplugged that. I am going to replace that today, but even with that unplugged it still does it. It was raining today, do you think this is a sign of water in my intake? any advise would be great.