Blazer sluggish initial acceleration?

My 1999 Chevy Blazer has been acting up and I can't figure out why. If I stomp the gas at a stop light, it accelerates slowly and the the rpm's rise as if I was barely touching the pedal. However when I'm at say..30mph or above and I have to hit the gas..it downshifts and accelerates with ease..as it should. I'm just puzzled as to why it does this at low speeds..almost like there is a governor. Any thoughts???? And to my knowledge there is no traction control..so I don't think that is the issue. Thanks