I just got my PPH's of Sam at socaldakota.com. I had the headers and Y-pipe ceramacoated and i put a single 3"system to a flowmaster super 40 muffler exiting out the side in front of the rear tire. I originally had JBA ceramacoated headers on and they rusted and chipped so i put the manifolds back on then i got the PPH's. I have to say that the PPH's with the 3" single side exit with no cat has WAY more pull and power than the JBA's. I don't know about the GSmotorsports. They seem like a good design but the only place that ever see's flow from your heads is at the top. So the compensation for the GS to match up perfect isn't really necessary but it isn't a downfall either. If you have extreme mods like a 408, supercharger, huge shot of nitrous then i would go with the GS headers cause they will flow alot more exhaust than the PPH's. Just think of it as a pro stock drag car, they are using large displacement engines and making huge hp so they use large tube headers to accomidate the extra exhaust comming out and the better flow. It wouldn't make sense to put small tube headers on a large displacement engine. Another thing is i don't think the GS's will mat up to the stock Y-pipe. they are to long. Then you have to get the Y pipe that they make. The PPH's come with a Y-pipe. And if you get the PPH's get them from Sam at socaldakota.com. He has great prices, awsome guy to deal with and his ceramacoating is top of the line.