My 2008 rmz250 after I fully rebuilt it (crank, bearings, OEM piston), along with porting done by MX-Time and all new stainless valves now has 7 hours on the engine. I always hated how easily the stock Titanium head-pipe dented. My original was dented severely after I was t-boned in a race, but it wasn't even a hard hit. A friend gave me his spare 07 head pipe. After a few races/rides, the front of the pipe was dented quite badly just from roost. I wanted to get the most out of my head-porting so I shopped around for a good deal on an exhaust system. I read the fmf 4.1 with stock header is what's preferred on the 08. My buddy with the 07 has the 4.1 with megabomb, no headwork, and I really like how his performs. I found a steal on a new FMF Speed Ti-Powercore and FMF powerbomb. The muffler is much lighter than stock. The headpipe is heavier since I went with stainless steel..... which as I said before, I don't like the titanium headpipes anyway since they dent so easy. Fit/finish is awesome. The muffler comes with a spark arrestor but I removed it before installing the muffler, I race strictly supercross/motocross. Also forgot to mention, my bike has a JD jet kit already installed, and performed great with the OEM setup. Sound seems to be about same as stock at idle and lower revs. It really barks though at upper rpms. I mainly ride/race at a tight supercross style track. The low-end power of the rmz works great for this riding but I was still in search of more upper power. I noticed off the bat there isn't as much low-end grunt. Low end seems soft. Exhaust made a good amount of noise, but it just seemed flat everywhere. There is no popping or bogging so I don't sense a lean condition. Fuel screw is 1.5 turns out complimenting JD's recommendations. Not very impressed with the performance of the setup. I'm going to try putting the spark arrestor back in, maybe mess with the fuel screw a bit. Might try removing the powerbomb and adding my oem header. Fit/finish great, some good weight savings, but the performance is just not there.