I have the Gibsons on my truck (QC). My Dad has a reg cab with stock manifolds. His is RC and mine is a QC. Both trucks have the same exhaust, Magnaflows with resonators removed, sans the headers on the RC. Mine by far sounds better. Both trucks also have the cats on them. They may not boost HP that much but they do make it sound better. Now we are also talking QC vs RC so there is a longer pipe length to consider if that really makes a difference.