As we all know the stock muffler on the 08 YZ450 is super restrictive. Here's an in-expensive fix, that boosts power. I took an 07 stock muffler, trimmed it back 5 inches, and installed an 06 stock end cap on it. Re-packed it of course, and on track benfits can be felt right off idle. This bike comes alive instantly now and revs out a long way, much better than stock form. Dyno runs even show a 1.5hp gain. Just wanted to let ya know if you can scrape together some old stock parts the 08 YZ450F will rip with very little work. Plus the bike definatley sounds better now, and revs much quicker. It feels like a completely different bike. Best of all it only cost me a few hours of work, and bag of 4stroke packing.