I have a 99 suburban K2500 4x4 with the 7.4L. I have ran a couple of different code readers to try and find out what is causing my engine to run rough and all they are telling me is the engine is running rich. I have been told by a couple of mechanics that the intake gasket will start leaking and cause this problem so I changed it out and found that was part of the problem. The gasket had failed and was leaking coolant, but did not fix all of the problem. Does any body have any ideas what else could be causing this problem. I have a k&n air filter that I just cleaned out and the plugs I changed out about 20000 miles ago.