My 1996 Suburban has 155,000 miles on it. I have owned it for 2 years now and just did the full tune up about a year ago. I noticed a slight and persistent jerk to it on the interstate, but it was so slight i thought maybe it was the wind. Within the last week it has been getting worse and worse and now its not just on the interstate. The wierd thing is it only happens when i am trying to maintain a steady speed, and if i feel it happening i can step on it and the engine responds quickly and takes off i just cleaned the throttle body out and put a can of sea foam in my gas but no impovement. It idles great at stops, has no problem starting from a stop and fires up right away when starting. I had a friend check the TPS sensor and he said there were no changes in the voltages when opening and closing the throttle...any suggestions?