My friend took a guy riding just today who acquired an 03 450 but had a stock exhaust (no sparky). They feared the rangers would nab him so they asked me if I could sell the guy a PMB tip to help him out. It appeared to them the endcap wouldn't fit so they just bolted the entire silencer and endcap from the 98 to the 03 and Viola. Yep the 1998 YZ400f rear portion of the stock exhaust can bolt up to an 03 YZ450f without any hassle. I just wanted to share for those that may find themselves in a similar situation.