Here is my problem. The M is cold and I start it up and drive down the road. Everything is good. Then a mile down the road when accelerating there is hesitation, my exhaust sounds like a drum roll. Then all of a sudden everything is fine and I get a burst of power. I slow down to cruising speed and everything is fine, then I accelerate and it sputters for a few seconds then the power comes back. I have replaced the cap, rotor, spark plugs, and fuel filter. My plug wires (Nology) are ~2.5 years old. I tested the plug wires and they seem to be fine. Any help is appriated.

Thanks,
Mark