Just to chime in, we don't have any check engine lights thus far. My kit included the hose with the pre-punched hole for the air sensor. It was tight to install but worked to my benefit once done.

We had to battle some exhaust leaks during the install process - but that is normal. Ended up completely disconnecting a couple joints to start over and get a better seal. Seemed to work well enough after and no leaks after several hundred miles of driving.

Pickles - My buddy has a smoke system for testing leaks which we'll use in a couple weeks. Short of that, I've seen people use homemade stethoscope-type devices to listen for them. Simply enough though..get a good light and look for any areas with black sooty dust near joints after shes cooled down. Too simple - maybe..but it can work.