ARH headers will make a significant difference for force induction installs. I picked up 22HP and 19TQ on a mustang dyno
over a catless xpipe I had before (VF 650 Supercharger, red line: Macht Schnell Catless X-Pipe and Borla ATaC Rear). The graph is a little smushed, but you can see I made power across the entire rpm band over the catless x-pipe I had before
Why do I keep mentioning the comparison was to a catless xpipe? Because some claim that simply removing the cats yields the same net HP increase as headers, this proves otherwise as I had no cats to start the comparison.
I'd also mention the quality of the welds, flange, and overall craftsmanship is excellent; no issues after 2.5 years. Customer service has also been fantastic. Sound is great, significantly less rasp, deep and throaty.
FYI do not run the flex fuel kit if you are boosted unless you plan on installing larger injectors and upgrading your fuel delivery system; stock can't keep up with the demands a supercharged motor.