If you guys are talking V8 or /6 I can tell you Charlie here told me this, all engines need back pressure, when I had my 73 Challenger 340 car I had unbolted my collectors and tighed up my exhaust to get a time on my car, plus the cool factor of open headers at George Rays drag strip.
Open headers ran 8.69 to 8.90. Then I hooked my exhaust back up and it ran 8.10 to 8.20.
Charlie advised me to run my two 1 1/2 " drop pipes off my /6 to a 2.1/4" single pipe.
Glad I did, no drone at all and a bunch more power at 2800 rpm threw 5000 ram
Is this what you guy are talking about ?
Its still early and in my first cup.
Oops ,I got two super nice coffee t-shirts yesterday !! Thank you to who ever made that happen. :thumbsup::thankyou: