[CobraEd]

Ed, Something about this is not right. If you set the mixture to match the exhast, you will always get more power with less restriction. Now "tuning" an exhast system can produce more power than an untuned system due to proper scavenging of the exhast pulses, but I would not equate that to "backpressure". Proper scavenging (tuning) is why no one runs the exhast right out of the heads. All of the fastest cars around the world in all the various categories run open headers of some sort with no mufflers or restrictions, but they do have their header pipe diameter and length along with the collector size tuned for their particular rpm range and use. Top fuel dragsters are the MOST POWERFUL of all cars (6,000 - 7,500hp) and they run large diameter, short individual open pipes. But again, tuning for scavenging is not the same as backpressure.

Maybe it's all semantics!!??

Ed