i have a nitro sport w/ pro.15. today i was driving it around and it startes to hesitate when accellerating mildly after about 1/3 of a tank. on the next tank it was hard to start and then wouldnt rev out for about 1/4 tank. then in just an instant it seemed fine again for about 1/2 tank. finally it started hesitating when accellerating till it ran out of fuel and i gave up for the day. any ideas what could be causing this? motor compression seems fine, carby well tuned, not running lean either. thanks for any help.