Here is the full installation of the Soul Competition headers on a Porsche 981 GT4. I kept the factory PSE mufflers on. It sounds awesome this way. I wouldn't do anything else to the exhaust. I maybe missing some horsepower as compared to the other company headers out there, but for the cost difference 2k vs almost 3-4k for others. That cost difference doesn't justify trying to get the few missing ponies that the other companies have.

I also did the spark plugs as well. I would recommend removing or lowering the headers a bit to service the spark plugs. It made it so easy. After having all the tools handy its only about 30-40 min per side to remove the header to access the spark plugs. It wasn't to hateful.
I changed the plugs at 4 years and 5300 miles. They looks fine. Honestly since I garage the car the plugs would of probably been fine for another 2 years.