I'm not sure which year your 4.8is is, but most of the problems on the '04's had to do with a control module that would fail over time. At some point in '05, the module was updated to a new part that worked better and didn't fail nearly as much. Using inpa to reset the module and then going through a few rounds of ride height calibration usually does the trick unless you have real hardware issues (leaking bags or bad height sensors). Personally I like the sir system as long as it works as it should. It gets a bad rap because most people don't know how to get it working properly when it goes out.