My friend has a 2 into 1 Carb and loves it . When you get technical the dual carbs on your banshee are on and off. and with a single it's drawing fuel all the time making it more efficent in low and mid. but hardly a noticeable difference on top end. as for the www.dynoport.com 2 into 1 pipes they do sound really awesome ! I have had Toomey T-5's which sound great, but the dynoport sound way better. They have a great powerband that you could ride all day and not the lightswitch powerband of a Toomey.

 

I have the single Kiehin 34mm on my Banshee. Engine has fresh .040 bore with Wiseco pistons and old FMF Gold Series pipes. Otherwise it is stock.
The Quad came with this when I bought it, so all I can compare it with is other Banshees that I've ridden before.
First, it starts on the first kick, then has a noticable improvement in bottom end and mid range. The power band is much longer too. The top end does suffer a little, but with the midrange improvement, I can live with that.
In short, I like it. And, for my needs, I'd buy another one.