Yea, I suppose the tooling could wear and the personnel could have different ideas on what is quality work.

You'd think if a header on an engine on a stand would clear the filter in 2009 the same header built by the same company/factory in 2019 would at least be close enough to clear the filter. Parts of the car are a different thing. Motor/ tranny/body mounts saging, new or replaced with aftermarket, can alter the position of the engine in respect to car parts. I couldn't find much searching for this here, but I googled it and found piles of FGF site threads on this very subject, some with me posting that I forgot about. Seems a Doug's header will fit great for one guy and not worth sht for the next. Big gamble at $800+ a pop.

I posted my Doug Thorley headers fit well, they looked that way when I bought the car. After installing new body mounts, changing the transmission crossmember and mount, engine mounts, changing transmission and removing then replacing steering components the header seemed to be closer to the steering box than before. Bashing it seemed to be the only fix.

I found about fifty posts from different sites telling how the Doug's headers didn't fit without bashing the tubes and/or the floor boards or having to use a remote oil filter. Only found about 10 who said they fit right up without clearance problems. About five of those without clearance problems said "except this or except that" they have a different definition of clearance problems than I do.
More post about bad fit than good fit could be because people tend to say more about what went wrong than what went the way it's supposed to..

Don't know what to do now, not like you can go to the local muffler shop and keep trying different brands of headers until you find one that fits just right.