How much actual difference between the Fatcat system and a set of good flowing slip-on mufflers on the stock headpipes?

 

In terms of what?

Noise?

HP?

Torque?

Appearance?

Weight?

 

You forgot...

Flow?

Heat Dissipation?

Ground Clearance?

Total Length?

Amount of Phenumonoultramicroscopicsilicovolcan?

 

Big difference in my opinion..... not sure if it was a softail, but I seen a guy on this forum put in SE 204 cams with the stock headers and some slip ons and then changed the pipe to a Fat Cat and the two dyno sheets were chalk and cheese with the fat cat making a big difference to the numbers and the TQ curve especially. A good pipe is a must if you are really concerned with performance.

 

The question was related to HP and Torque. How much and on what end of the curve or throughout? Dyno only difference or very noticable while riding?

 

It depends on what slip ons you use too.I had the old screamin eagle II slip-ons on my fatboy then changed to a V H Propipe and lost performance.