$1k is tempting.
As far as a warranty goes, I had a big block SCJ Mustang back in the day and put a set of Hooker headers on that animal (while not stainless, they supposedly were the top of the line at the time). It wasn't the crack that appeared after 6 months that pissed me off the most. It was the bitch of removing the headers, waiting for the replacement set, and reinstalling them that was the real pain. If you think a 55 is tight under the hood you ain't seen nothing.
I also used to tune two strokes for a living so I also have a fairly decent idea how a four cycle exhaust system works.
I haven't gotten too deep into the variances between brands, but for me installing the log design, while slightly better than OE, is a waste of money and labor for the designs return on investment.
On the tube to collector designs, some have a longer primary tube than others, seemingly for better mid range torque at the expense of high RPM power, one in particular that uses a long tube also has a larger primary diameter in the attempt to bring back the higher RPM power and still retain more midrange torque...
Did the guy at Kleeman mention that most of the tube to collector designs also seem to use the larger collector diameter? I would need to look closer to verify but this is likely the case. That could explain why these companies also want to sell you their entire cat back exhaust kit with their headers. Cha Ching.
And that leads to the million dollar question. Of course there is the CEL issue. What options are out there if the header length (and collector diameter) causes the removal of the OE cat? Would that make a header that uses the OE cat's tube diameter all that bad? How do these folks address the CEL issue?
Typically a good set of headers on a performance oriented N/A motor are worth 8%-10%. On the same motor, a smaller collector size is likely to put you closer to the 8% side of life. Does that mean I'd have to sacrifice a few HP to avoid spending another $4000 to buy someone's complete cat back exhaust system? I might could live with that.
If I was going with a blower where the smaller collector would really be a bottleneck, I might be thinking differently. Anyone have input on this?