I've researched so much here while looking for my 64 vert, I can't remember what I've read. Isn't there a need for some exhaust back pressure to keep the engine purring, or is that on turbo mods?
Back pressure is never good, turbo or not. Lots of guys think that back pressure helps with low end torque but that's not true. Whatever they experienced to make them believe that was a misinterpretation of what was really going on!
