I've had my Flowtechs for over a decade now. Originally they were ceramic coated, not that good looking but I think that is what has helped them to stay in one piece. For the 230(iirc) i spent it was well worth it. They fit fine, although if you compare them to newer flowtechs you can see the design has changed.
In a performance application I will not run anything short of longtubes, besides I don't have any real issues with them and it's easier to run your exhaust off from.
That said, I have ran the Advance Adapters headers on my S10 with the same engine that's in the Malibu now. They fit great and were very easy to work around, but they had to have hindered performance. I wouldnt want to try to run them on anything making more than 350-400 just to make sure your not losing a lot of power. Also they make look cheap but they held up quite well. I can't count the times I had them glowing red due to issues I was having, and never had one crack.