I noticed that even after my truck is nice and warm or has been driven for a while if i put it in park and it sits for a couple minutes the rpms will drop and kick back up to normal but my afr jumps and stays at about 16-17 and gets a slight lope. if i leave it unchecked my truck will die. thought it was perhaps a bad tune so i redid my tune and nothing still happens. it happens everytime not just once in a while. Any ideas?