Not to say you guys are wrong, but it does sound like a few of you work right for Harley. Yes you need back pressure. Most dealers would cut your baffles for you before all the EPA Laws for 2006 & after.
My bike is a 2001 & I have no clue what pipes are on it as I was not the original owner. I removed the baffles & stuck some Big City Thunders in their place. My bike is much louder & as far as performance, it was Dyno'd. It got much better results then any stock bike. Really your bike should have as many horsepower as your cubic inches of the engine. Mine is 88" & I have 86 HP. A stock 88" would have about 20 HP less. Besides the pipes I just have a high flow air cleaner. If I gun it up to about 80 & then release the throttle, I will get some backfiring. No big deal because I am not usually trying to get to 80 as fast as I can & then letting off the throttle anyway.
The main problem is, you have a 2007, so that will change everything. Most dealers won't do alot to it because of the EPA laws now. My wife has a 2006 Sportster 883L & it had some engine issues. The dealer wouldn't do to much because they were afraid it may cause issues with the EPA. I told them, sorry, it is a 2006, the law is 2006 & earlier are not included, & it is still a choke not fuel injection, so it for sure is not included.
Here is a good link to Exhaust Reversion
Understanding Exhaust
Here is part of it about "back pressure" which is NOT as important as alot of people want you to believe.
"Much controversy (and apparent confusion) surrounds the issue of exhaust "back-pressure". Many performance-minded people who are otherwise knowledgeable still cling tenaciously to the old school concept.... "You need more back-pressure for better performance."
For virtually all high performance purposes, backpressure in an exhaust system increases engine-pumping losses and decreases available engine power. It is true that some engines are mechanically tuned to "X" amount of backpressure and can show a loss of low-end torque when that backpressure is reduced. It is also true that the same engine that lost low-end torque with reduced back-pressure can be mechanically re-tuned to show an increase of low-end torque with the same reduction of back-pressure. More importantly, maximum mid-to-high RPM power will be achieved with the lowest possible backpressure."