I purchased a set of DNA stainless steel headers off ebay but read up on them before buying so I knew what I was getting myself into. The DNA headers are/were exactly the same as the OBX branded headers without the pretty little stamped OBX brand plate tack welded to them. Issues with them - runners weren't aligned and welded to the mounting flange correctly, ports in the mounting flange were massively undersized (I'd read comments that the headers actually caused
lost engine power when installed) and some buyers even stated the mounting holes didn't even line up with the exhaust studs on the head (this could have possibly been due to the wrong headers being shipped) and the flex joiner section being too short to bolt up to the factory exhaust.
These headers cost me $63 USD to buy (at the time I purchased them) Cost me more in shipping than the headers themselves... they did however come with gaskets and bolts (bolts were pretty much junk too but the gaskets were decent quality) I invested 2 weeks of grinding/modifying/polishing into them before installing them on my J2 Sportswagon to correct some of the manufacturing faults.
I ground out the ports to the absolute biggest diameter I could to match them to the inside of the exhaust runners and then polished them as smooth as I could (see this post on my thread
here) At a guess I'd say it was possible these headers were actually factory seconds. To me it looked like the runners moved while on the welding jig and it gradually staggered the pipework out of alignment with the flange. The openings on the runners are slightly flared. The other issue was pipe overhang inside of the collectors. These headers are a 4-2-1 design and the only place I could reach to rectify the overhang was the secondary collector where it joins the runners together before the collector flange. The overhang was significant and if left in the collector, it would've caused some serious issues with exhaust pulses favouring one side of the collector and messed up engine tune. I had to get in there with an extension shaft and a grinding stone and carefully remove the excess pipe until it was ground back to the contours of the welds without hitting or breaching them.
The effort was worth it considering how much they cost me + wrapping them with header wrap. Good, useable gains in torque and HP. Fortunately they fitted correctly without any need for cutting/welding extensions on them to make them fit. The flex joiner hooked up to the remaining factory exhaust perfectly however the cheap, small flex join failed 3 months after installation but luckily I had a new heavy duty 6" flex join in my pile of spares and junk to replace the failed flex. It still worked out cheaper by a long shot to buy cheap headers and rework them than investing in something like the Shark Racing, Pacesetter or OBX branded headers (especially the OBX as it seems like the little brand plaque added $100 to the price tag)
