I ordered the Laser Pro Duro together with the Dynojet jet kit and K&N filter from Fred Hink at Arrowhead Motorsports. But due to typical handling by USPS, I received the Laser exhaust a couple of days before the jet kit and filter.

Not willing to wait, I installed the Pro Duro first. This is on a stock 1999 KLR650, stock filter, stock jetting. Installation was simple, but the intermediate clamp provided is too big and needs the 1 7/8 OD X 1 3/4 ID muffler bushing that others suggested getting. I had some leftover cut-your-own header gaskets that I lined the inside of the clamp bracket with, and this seemed to work well enough. Once everything was tightened and put back together, I took it out on the freeway. With the stock filter and jetting, the pipe is only a little louder than the stock one, but the sound is deeper. I felt a little difference in the performance at low- and mid-ranges, but the freeway blast at high-speeds felt like the high-end range was the same. So just as a slip-on with no other changes, performance is definitely improved (though slightly). Personally, I think its deeper tone is itself reason enough to get the Pro Duro.

When I installed the jet kit and K&N filter, performance on the bike kicked up another notch. I put in the Stage 2 jets and drilled hole in my airbox for better flow to the new filter. With both modifications, the Pro Duro becomes a little louder, especially around the 6K rpm range, but still well within old-fogey tolerance levels. It sounds almost like that of a V-Twin (Ducati or Honda, not Harley). Low- and mid-range power is noticeably even stronger, with the top-end being a little better also. The bike definitely runs cooler and revs more quickly. Following the Dynojet instructions for Stage 2 jetting exactly, the bike runs well with no backfiring or surging, but the Pro DUro tip is a bit sooty. However, the new power is fantastic! It's no R1 (obviously), but I think my KLR is now quicker than my two-stoke RZ350 (and this is no slounch bike!). Might even be worth doing a trackday on this bike now!

I highly recommend the Pro Duro, whether you plan to re-jet or not. It does make a performance difference and it looks and sounds superb!

On a separate note, I got the MAP Engineering oversized braking rotor and Progressive fork springs from Fred also. Along with the Galfer SS lines (previously installed), the bike stops like a streetbike should now. If you primarily do streetriding on your KLR (as I do), I suggest getting the braking and fork enhancements first. It's better going fast when you know that you can stop in time!