Slip on HMF

[Tech23]

Realistically, what would the HP/Torque benefit be on a stock "99" 400EX With an HMF slip-on muffler[Properly maintained, and jetted].I am not interested in sacrificing ANY low end torque.Can the HMF deliver across the board HP/Torque increases?Anyone know of any magazine articles/comparisons on Slip-on mufflers?Any with Dyno charts? Thanks.

[Doibugu2]

I just put mine on a couple of weeks ago on a stock quad. It made a reasonable difference. I would guess 2-3 hp. I didn't loose any low end, if anything gained some. They are loud though.

I had my first race yesterday and I don't know why but my quad with just a slip on pulled on a lot of quads.