btw sound doesn't matter, 90% of your exhaust tone is going to come from your exhaust piping, muffler, and cat...

the oem style 4-1 manifold is what's called a 'log manifold' bad flow, but popular for turbo applications because it is so compact...

the 4-1 manifold you are looking at isn't bad, but the flow is much better with a 4-2-1 setup... The exhust pressure from the cylinders equalizes itself when it's coming out...

there's no such thing as a 3-2-1 setup unless your running a three cylinder geo metro... lol

the numbers represent how the piping reduces...
4 exhaust cylinders-go into 2 pipes-and then those 2 pipes reduce into one...