I was thinking that but looks like only a 20 HP gain from the stock heads to those according to the magazine articles where they tested them..The RPM was 20 more HP on top of the stealths, then the TF was 20 more on top of the RPM..
The thing that many don’t understand is, it’s not a guaranteed fixed gain between those various heads.
The milder the build, the less the demand placed on the induction, the less difference you’ll see with better heads.
The opposite is also true. The higher demand on airflow……the more the better heads will pay off.