OK...do some digging. Lots of info out there about DL's needing backpressure. Straight pipe =/= open header. Without backpressure, these bikes lose power. You also run the risk of running it way too lean unless you put it on a dyno and tune it do dump enough fuel in. I haven't seen a single Power Commander map out there for an open header.
When I was looking for low mount, shorty cans for my bike, I called D&D and gave them the specs I wanted. They wouldn't even consider it unless I was willing to pay them to do the R&D to test the design for adequate flow and backpressure. I ended up having Coffman's in Cali making me a pair (no R&D involved). I gained a whopping 2 HP over stock with a noticeable increase in fuel consumption after dyno tuning.