Thinking about slip ons, which brand?

[lone wolf in canada]

I have the Sreamin Eagle Fat Shotz and love them. I added 3 rings per side and I can feel the increased power I seem to get in the higher RPM of the gears over stock pipes. Louder than stock but the wife doesn't complain after an hour on it. They really bark when you accelerate. Also they are 50 state street legal and up here when we run to Quebec the cops are always following you re the loud pipe thing they have there, and these have that stamp on them, no worries. I've heard Ontario will soon be going like California with noise on bikes and I don't need to buy pipes stupid loud that I have to change again.

 

[WillieB2011FatBob]

I just bought my 2011 Fat Bob and am very disappointed with the sound. Not looking for more/better performance but the "Harley sound" back that I got from my 2001 Low Rider that just had the baffles 'drilled out' when I bought it.
If I go with the Screaming Eagle slip on's, do I have to make any mods to the engine so that I don't lose any performance?? I LOVE my new Fat Bob's throttle response and power and don't want to lose that.
Thanks all.