O2 sensor's
 

I have a crack in my header that is not repairable. I am waiting for a set of Kooks to arrive. The Injector banks are noticably different. Would this be caused by my leaky header? I don't want to start any tuning until I get the new headers in but I would like to get the car running better. The idle is holding up until I come to a dead stop. I used the smoothing feature in HP tuners and that cured my idle problem but only for a short time and now the car is back to running at 2000 rpm until I come to a stop. Any sugestions.

If you have an aftermarket cam in it, you may need to adust the throttle follower/and airflow tables to allow for the cam. Not exactly sure which tables to use in HPT, still working on that for one of my cars, but my 00 Z had that issue, "cruise control" type and tweaked the RAF and follower/cracker tables, and it was very nice.
Yes a leaky header, and gasket will skew the IPW as well since the O2 gets doeses of fresh air.