A few weeks ago, I had to have my entire exhaust redone to be able to pass safety and emissions-compliance(no testing) due to my previous work I had done was in terrible shape.
My previous setup was JBA ceramic coated shorty headers for a JGC 4.7 that I had gotten off here, then a custom made compression bent Y-pipe to the factory cat and then a compression-bent 3-inch cat-back system using a Flowmaster 44-series muffler(wouldn't have been my choice, but the shop made a good choice afterwards
The problem with this setup is that I had to use aluminized steel and the gauge they used was not very thick. Since I was living in Kansas a few years after I got this done, I didn't have any indications that there was any problems with my exhaust and when I was told that there were multiple leaks, I was stunned but not shocked because I knew I was going to have to replace this system at some point. The cat-back had rusted out at the hangers and was barely hanging on. The Y-pipe was very rusty and may have had a bunch of pin hole leaks just from looking at it. But, the worst was the headers, as one side had a cracked flange and one of the tubes was leaking as well. I was not happy about that, especially since a new pair of ceramic coated headers from other brands that still made headers for this engine and truck are $600+.
I ended up working a lot of overtime just so I could get this done as soon as possible but it still took two months to get everything I needed to be street legal.(Not wanting to boast, but I had been driving around illegally as I had not gotten my registration stickers
My new setup is as follows: Gibson stainless steel shorty headers, Magnaflow direct fit catalytic converter, and Magnaflow cat-back exhaust kit.
After driving the last two weeks, I noticed that my fuel economy went up. More than likely, the PCM was detecting extra oxygen and therefore richening the fuel/air mixture to compensate. Even though it wasn't a big increase, it was still noticeable, especially when I was at half a tank. The sound, though, is very different from what I had previously and I was a little disappointed that it wasn't as loud, especially under no load idle and it sounds like many other trucks now with an aftermarket exhaust. But, since the install, I have liked it more and more.
Moral of the story, don't even bother with buying a custom system with aluminized piping in 4 seasons areas, it won't last and will cost the same as aftermarket stainless steel system.