70 dart 470 ci drag car build.

MOPARMAGA said
I should have remembered to post that both afrs worked the last couple pulls.
You make some points that made me think.
We have a 6inch exhaust system that lays on the ground with big semi tractor mufflers on the end.
There's so much exhaust pulse reversion coming back out of that pipe that's hooked to my collectors so there's air definitely getting backed up and the point of the 02 sensor

This is from Jere Stahl's (of stahl headers) website. I don’t know if the site still exist. There was lots of helpful information about dynoing on his site. I copied it into my dyno book when researchinghow to build my dyno. Here is what he had to say about dyno exhaust. For what it's worth.