What's driving me bat-"*)&" crazy is that the Magnaflow ones I showed you all are claiming a 15 hp increase and they're even using the original space for the primary catalytic converters - maybe it's the huge collector? I've found on my Chevy Prizm that a huge catalytic converter brought it form 59 wHP to 90 wHP. The magnaflow would be the simplest of installs of them all...but it's just too pricey. At about $1,200 I could be $900 into having my Chevy Prizm back onto the street which has a long list of mods. Then my truck could stop being used for commuting except maybe once a week to keep it up, bring some tools home for the weekend, stuff like that.
I tried after my half of a night of studying on what other people have done to find some dyno proof of any of my ideas (I was honestly very sick last night and these wonderful header studies kept me sane, thank you to EVERYONE for their comments and those who are listening in!). The closest I could get was on the next generation of Frontier from 2005 and up to some year. Now their engine bay is kinder to them (I guess based on what's available to them), and whenever I see the available headers for them I'm jealous - tuned headers are available, but yet, 1 dyno chart shows mid range to upper range power increases on headers which weren't tuned. Once the 4.0 saw a tuner as well, they got the power back on the low end (there was some O2 sensor confusion) and increased power again on the rest of the curve.
While extremely impressive I'm comparing maybe a gaila apple to a golden yellow. They're quite similar, but different engine, easily different results. They're both delicious but one is stronger. Gaila's are firmer so they're the 4.0 and the Golden Yellow is my 3.3L Frontier, lol.
I almost forgot the most important part! On the Frontier with the 4.0, the headers was the single most important power and efficiency gaining mod. Yes, full systems help, and intakes and all that, but they're all frosting on the cake of those headers.
Yes, plans are in play for other mods, but to me those are less complicated and confusing. And thank you. I have studied about pulse wave tuning and what not, but you're explanation of why equal length primaries just works really made it finally make sense to me.
In brief, since you're curious, I plan a cheap short ram intake for winter driving because the cold air is murdering my gas mileage. Hey, if it improves flow great, but the stock cold air intake would go back on when things warm up if funds aren't available for a cold air intake. I know how much hot air doesn't help with power, but I also have proof on my extensive testing on my Chevy Prizm that you can have too cold of air for efficiency to the point of it being power robbing. In fact, you can check it out on YouTube. ::wink::
https://youtu.be/SfTcm3J92E4
I also have a Flowmaster muffler if anyone knows if they're any good. I think it's a delta 40 if I recall correctly. I originally bought it for my Chevy Prizm, but Flowmaster said that it helped cars most if they had at least 24 more inches of piping after the muffler. That was impossible on my Chevy, and I was already pretty happy with the Magnaflow muffler (It looked to about rust through being aluminized steel, but apparently it's life time warranty so...) This Magnaflow muffler is mid sized SUV rated muffler may just belong on my Frontier to spice things up, without getting crazy noisy. >
My Chevy Prizm by the way for its first year or 2 after the cat back exhaust was so loud all my friends knew I was coming a couple blocks before they could see me. It calmed down, but it was way outside of my comfort zone. I wore ear plugs for the first year before carbon quieted things up...I'm not going through that again, lol. I'm sure I lost some down low torque and power before other mods woke that part of the car back up, but I got 55 MPG on the freeway in September and October on a monthly 313 mile trip. 44 MPG uphill and 55 overall down. Stock that car should do about 27, lol. Also, maybe I got lucky, but when I was done with her the torque app calculated based on OBD II data, that I had taken a 45 wHP car up to 117 wHP at it's hey day.

I'm expecting less results form the Frontier, lol. The Prizm supposedly had 126 hp at the crank, but if so the factory really de-tuned the poor girl.
Sorry that was short story long. Can't help it. Loved the success of it.
@shift_RUSH, thank you! Now I know that Magnaflow could last longer with some paint. I thought it being aluminized would help it from rusting, and I suppose it did, but it really didn't fare any better than the mild steel piping going up to it . . . maybe it did worse.
For some reason when you say back in the day, it makes me think 80's trucks because those were the vehicles, which I first learned to change oil on, but not much more. If so, at least by their labels, header paint can take about 900 degrees more F than what I saw possible in the 90's (based on me just perusing at AutoZone's paint)...which basically made them barely good enough for a muffler if you ask me. 1,400 degree paint would have to be more than good enough since catalytic converters start bronzing at 1,000 degrees. They're not supposed to get that hot either. It's how they know they won't be honoring your catalytic converter warranty because you burned it up with misfires or something. And Catalytic Converters get way hotter than headers...at least on the cars I've shot my touchless thermometer at.