Lexus forms very nice D ends that stretch the 50mm pipe to half a 60mm D shape. Lexus swages the 60mm to go over the two back to back D pipe ends and welds up the assembly. Works nicely and is STRONG. I see using the merge collector design as superior and there are good calculations for pipe sizing already available not to mention factory style would be very difficult to copy without specific metal working equipment.
Where does Lexus use this? Ya got any pics?