Good question. Are you referring to the "Y" as meaning the resonator, where our dual 2-1/4" tubes dump into the resonator(SRT6)? It is my understanding that industry standard suggests that you should have both banks of the exhaust equalize sooner, rather than later(waiting for the exhaust pulses to reach the resonator). Thus, the H-pipe they gave us mid stream. The newer X-pipe research suggests that it is a superior performance enhancement for better exhaust scavenging / flow. I'm just following the lead of others that suggest this is the better performance decision. To explain the physics of why this is better, needs to be shared by someone a lot smarter than me.