Having issue while driving along in cruise control or just at a idle speed not pressing gas just idling along at 40 or 45 my RPM jump up and down 400rpm and can feel truck trying to give itself gas when doesnt need to be. at cruising speed. I changed some cracked hoses but still having same issue. Please help took to mechanic they still researching but any help on to what may be causing this. Its opposite of bogging out is whats happening. Thanks