We went to Racetown395 and it is one of my favorite tracks. Many different types of obstacles and dirt that ranges from sand to hard pack. I'm a 50+ mx'er and certainly no expert in mechanical engineering!!. There are few things that give a motohead as much excitement as adding some brand new BLING to the scoot, especially something that would make a difference in performance...such as an aftermarket pipe. Comparison: In order to be as abolutely unbias as possible I wanted to take some laps with the stock pipe on the bike and then change to the Big Gun pipe. That way I could see where the differences were between the two pipes. I also run VP Red mixed 50/50 with premium pump. Stock pipe: Fitment is without question the best. I honestly believe the stock pipe is good. Generally speaking, the late model Yamaha's (especially the fourstrokes) have months of R & D in them. The stock pipes are good for the general masses and that is what has to be when building tens of thousands of bikes to be sold world wide. As usual, I was impressed with the stocker and it has good transition from bottom to mid. However, even with jetting changes it seemed to lack a good transition from mid to top and didn't seem like it would keep pulling hard to the top. Not that I can constantly ride a 450 at the higher rpm ranges like CR or RC but for those time when it is necessary I thought it could be better. Big Gun: Fitment: It is a 3 piece system, head pipe, mid pipe and the muffler. Fitment is what I would expect from Big Gun. The only thing that needed attention was a hose clamp on bottom of the hose that runs into the water pump. The area where it tightens rubbed on the head pipe. All that I needed to do was loosen the hose clamp and spin it around. The head pipe/mid pipe fitting was tight. I used some red silicone and that not only sealed the junction but allowed the mid pipe to slip over the head pipe much easier. The muffler to the mid pipe was a no brainer. All bolt holes lined up properly. The exhaust flange is much thicker than the stocker and I would recommend replacing the stock allen head bolt with one just a few millimeters longer. All other stock bolts are ok. Sound: When I first fired it up I thought it was a bit louder than the stocker. Apparently, the packing needed to fluff up because it became quieter as I rode it. The Big Gun pipes also come with a 96db insert and a spark arrester. So, overall, the sound was about equal to the stock pipe. Jetting: Mike said no jetting changes would be necessary. I told him I had already jetted the pilot and main one richer and he said that would be perfect but they will run just fine with the stock jetting. The YZ-F's are jetted lean on the pilot and main this year so I had a different opinion on that subject. Never the less, with the jetting I have in the bike right now the pipe worked well. Very, very minor popping on decel. Mike suggested if I was going to ride with the quiet insert in all the time that I lean out the jetting a bit. Knowing my time with the insert in the muffler would be minimal, it was a non-issue for me. Performance: Bottom (low rpm): The first thing I noticed was the throttle response seemed to be a bit crisper. Nothing earth shattering but enough to notice the difference. My first lap out I took it easy because I didn't know what to expect. I did notice the throttle response out of the corners seemed better (crisper). Really low rpm chugging, that with the stocker would make me wonder if it would keep running, was not an issue. I could crack the throttle open from really low rpm and I had better be hanging on. The bottom end torque was improved but not dramatically over the stocker. Mid range: This is where this pipe starts to shine. The transition from the bottom to mid is smooth yet there is a noted improvement over the stocker. Even on the dry hard packed corners I did not get the feeling there was any extra wheel spin when exiting a corner. Torque also seemed to be improved over the stocker. Top end: I have to be honest here. A 51 year old MX'er rarely gets a 450 to the rev limiter. I did however, make it a point to do just that. The transition from mid to top was unbelievably better than the stocker. Where the stocker felt like it was flattening out during this transition that feeling was completely absent with this pipe. There was a rolling whooped straight that was WFO for about 100 yards. With the stocker I was tapped out in 4th at the end. With the BG I did the same straight in 3rd and hit the rev limiter at about the 1/2 way mark. The bike pulled hard all the way to the rev limiter. The next lap I came out of the corner in 3rd and immediately shifted into 4th. By the time I got to my normal braking point I was still pulling hard in 4th and not bouncing off the rev limiter. Good over rev. Overall: I'm pleased with the total performance of the pipe. Because of my impression of the stocker, I'm most impressed with the mid to top power. The head pipe and mid pipe did discolor to a brownish color. I'm not sure that with the heat these bikes put out there is any way to avoid that. Sorry for the length of this report but I wanted to try and cover all aspects.