I have FRPP sports. By looking at them, I know they are stainless steel. What kind, I don't know. They have been on my car for nearly 2 years, with no signs of corrosion. Sound is as good as it gets with a V6 IMO.
As for cost, yes they are expensive, but they do what they are intended to do with no guess work.
I got mine at American Muscle when they were on sale. and I also got the forum discount. You can watch their site for sales, or just go and buy them. Either way, well worth it.
2011 GT. Grabber Blue. Procharged. 3:73 manual.Billit LCA's. Corsa Extremes. GT 500 wheels. Racemaster DR's. T-56 Tremec. Dynotech DS . Centerforce DF. American Racing headers/high flow cats 560 rwhp.Donny Walsh tuned
2012 Pony Package. Race Red.3:31 automatic.BBK longtubes and catted X.FRPP Sport axlebacks. BBK throttle body. Dynotech DS. Brembo wheels and tires. Strut tower brace. Airraid CAI. Bama tuned.