I tend to agree with most of the comments, in most cases there are modest HP increases, however, as with porting It is my opinion that you do these mods to move the powerband, for example a beginner would like more bottom end whereas a pro would rather have mid up powerband. The manuf build a quasi all around powerband typically not awesome anywhere but good everywhere. Pipes and porting can move the powerband to the awesome level for a given range. So ya they do add the bling factor but also can contribute to a better running bike.