Do aftermarket slip-on pipes actualy make a difference?

[jagter]

Do aftermarket slip-on pipes actually make a difference in terms of power?  Or is it mostly just sound?

It seems to be the first thing most guys buy when they get a new bike.  Any experience out there of it actually making a measurable difference in power? (dyno graphs etc)

They weight savings seems like a good advantage, but from what I can see the power difference is mostly negligible.

 

[IceCreamMan]

 

[Wild Blue]

 

[iamgigglz]

 

[upsidedown]

 

[Wild Blue]

 

[KaTuM]

 

[subie]

 

[jagter]

 

[subie]

 

[jagter]

 

[ianb]

 

[heti]

 

[Vlakhaas]

 

[zacapa]

 

[paulb]

 

[gwild]

 

[Shaun]

 

[alanB]

 

[Vlakhaas]