I've been in R&D for 40 years for the big 3. Won't say which company. We share information. Yes it was factory exhaust. The numbers were on the high side. But still real Dyno data sheets.
I don't believe those numbers were on the high side at all. I really feel stock exhaust manifolds as good as they were on a 340 just choke the everliving s*** out of a six pack equipped motor as evident in many Dyno sessions
