WOW!

There are no less than 3 threads on this subject now and some very experienced members have weighed in. And that's not enough.

The ONLY way anyone will know about the difference between headers and manifolds....ON THEIR ENGINE.......is to test both....ON THEIR ENGINE. Change anything on that combination and you will likely change the results. So, anybody else's test may or may not have any correlation to your combo.

I think most here will agree that headers USUALLY add some performance to our Mopar muscle cars. Maybe not always (although they have always added some amount of performance when I have made the swap) but usually. The only real question is, how much. And again, that will vary greatly with the particulars of the combo.