I put a Dubach Racing DRD NS-4 exhaust on my KX450 and it was the same way, huge weight savings broadened the power and added alot more mid and top. Like drastically. I used a DRD pipe because a 2016 KX450 I bought used came with one and it was incredible on that bike as well. I was shocked because all you ever hear about is FMF and Pro Circuit but other brands are maybe as good or better