I recently bought a 2015 Forty eight Harley. And I want to buy an exhaust. I want to get the Bassani sweepers http://www.revzilla.com/motorcycle/bassani-radial-sweepers-exhaust-system-for-harley-sportster-2014 but until then I've been thinking about just taking the stock slip ons off and putting a custom down exhaust tip on the end of the straight pipes. Just wondering if that will work for now.

 

I wouldn't be doing that to a new bike (under warranty) just yet,,
That's a pretty drastic change and opening a lot of air.
First HD?

 

Loss of backpressure usually means loss of low end TQ.. and extremely loud, IMO, I'd just put some decent muffs/pipes on and go from there.

 

Why don't u try either SE or aftermarket slipons. Thats fairly cheap and may get u by for now.

 

I wouldn't, but not my bike...have you asked your dealer for advice?