First a little personal history. Sit through the rambling or just jump to the pipe review on the bottom. My last bike was the 2006 450. For a long time I was convinced that was the best bike ever made but after two years on the it I wanted some fresh wheels with fresh suspension so I planned to upgrade to the 2008. For a change I actually got to ride one before plunking down the cash. I was totally disappointed with the bike. Yamaha had ruined the perfect power plant and replaced it with a bike that needed the clutch fanned to get out of the turns. There was dead spot in the bottom end that was unacceptable for my riding style and speed. I decided then and there that my ’06 would be my last Yamaha. Thanks to this forum I have read over and over that the muffler was the culprit and there was a great bike hiding under there somewhere. When Yamaha came out with the $750 dollar rebate I decided that it would cover the cost of a new exhaust system. Still being frugal I found a new 2007 complete exhaust system on ebay for cheap so I picked that up. I purchased the new bike out of state and my 73-year-old father picked it up. It would be a month before I could travel to his house and pick up my new ride so he had a month to ride it as much as he could. BTW - at 73 he is a local moto hero and handles a 450 like you wouldn’t believe. He also rides a 2008 RM450 of his own. You may have caught his picture in Sports Illustrated a few years back when they did an article about a big race at Muddy Creek in Tennessee. They did couple of paragraphs about him because he was the oldest guy racing and he was beating guys a lot younger than him. Anyway him having the bike worked out good for me as it would already be broken in before my first ride on it and he is pretty good at getting the bikes jetted in too. He also hated the power curve on the new Yamaha so it wasn’t just me. Sorry I might have been rambling. Now the pipe test . I now have in my possession a new 2008 YZ450F and three complete Yamaha exhaust systems. The stock 2008 system that came on the bike, a complete 2007 exhaust system that I bought on Ebay and the stock exhaust system that I borrowed from my 2006 bike One moto with the original pipe reminded me of how bad it was compared to the ’06 engine. It just took a few minutes to replace the '08 pipe with the ’06 pipe. The first moto with the ’06 pipe told me that the reading this forum isn’t a waste of time! The ’08 bike with ’06 pipe was completely different. Like it just woke up. It was very strong right from the bottom and the power curve was so linear that it felt like an electric motor. I was on hard pack and it was close to perfect for the slick conditions. On to the 2007 exhaust system. I really thought that I would end up with the ’07 pipe on my bike so I would test it last and not have to change it again. At least not until I come across a good deal on an aftermarket system. I was so wrong. I couldn’t believe the difference between the ’06 and the ’07 systems. Where the ’06 pulled strong throughout the entire rpm range the ’07 hit harder on the bottom then just fell flat on it’s face. It made the noises and went fast but it didn’t pull worth a darned down the straights. Hondas were even able to keep up. I simply couldn’t wait to get the ’06 system back on the bike. There you have it. A seat of the pants test for people that might be looking for the least expensive way to get the most from their 2008 YZ450F. Just keep looking on Ebay until you find a complete ’06 exhaust system and buy it. I only paid $150 plus shipping for the ’07 system and I suspect any ’06 system that comes up can be had for under $200. That’s way less than half of what an aftermarket system will cost you. Hope this helps, Kyle T FYI - I’m just over 6’ tall and weight about 190. I have over 30 years motocross experience. I made it to pro level and even qualified for and raced in a few pro supercross and outdoor races in the late 80’s. Never a star but at least part of the show. I think I’m faster now than I was back then too but I just don’t take as many chances. I know I’m in better shape.