I have a 04 Z71 Colorado 5 cyl, and have a fluctuation of the RPM at about 60 MPH, even with the cruise on.I have replaced the coil packs,plugs,cleaned the Maff sensor with the Maff sensor cleaner, checked /cleaned the air filter, checked for vacuum leaks( Only 2 places?) I have ordered a new Maff sensor and a Mapp sensor,but they haven't arrived yet. What could be causing the problem? The truck really runs great after the coil pack change,but seems to have improved after the MAFF sensor cleaning. I have no codes showing. Thanks in advance for any help.