Pipe design is quite complex and involves the diameter and lengths of tubes, crossover placements, resistance to flow, etc. But, it's obvious to me through my 'seat-of-the-pants-testing' of various pipes and setups that you do sacrifice low end as you go to an open pipe.
Most of us drive our bikes in the lower
rpm range, stoplight to spotlight, and that's where I found the biggest difference between an open pipe and a more restrictive design. Obviously if the pipe is too restrictive, you'll lose all-round.
When running straight pipes I found at
WOT the bike 'seemed' (it's all perception
) to have more power, but takeoffs from lights and roll-ons were terrible. As I increased the resistance to flow of the exhaust gases I found the was able to improve the low end. As I do most of my driving at less than 1/2 throttle, it has worked for me.
I also found that going from a 2 to 1 design to a 2 to 2 that I also lost a bit on the low end. But in this case I was willing to sacrifice some low end power for the look I wanted.
Life is full of compromises. It's up to you to pick the best choice for your situation.
Doc
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It's not the money. I think the 
It`s been said too staight and you loose
Hate when that happens. I've been thinking about taking a page from my first bike. 305 honda Dream. They had basically heavy washers at the end of the pipes on pivot pins. If you wanted quieter you rotated the washers so it closed off the pipe except for the hole on the washer. Louder you rotated so the washer was flat across the opening. It could work the same for back pressure. If i'm going to be tooling around town I can close the washers (quieter and better response) and for highway I can open them. I was thinking of about a 1 & 1/4 inch hole on the washer. Who knows. I might like it with the washers closed and leave it like that. Now that's my thoughts but I need someone to shoot holes in it if it would require re tuning every time I moved the washers. Or any other probelms you can forsee. Waste of time.......
