"Do the exhaust runners need to be the same length for max performance?"

The answer is yes and no. Yes if you are naturally aspirated because as the pulse goes through the collector and out the megaphone, it creates a negative pressure on the tube next to it to help scavenge or suck out the exhaust on the next cylinder. If your turbo'ed, the answer is no because you will always have back pressure and never scavenge to any degree that will make a difference. The size of the tubes should be the same as the area of the exhaust valve (or port), not bigger. Bigger diameter slows down the speed of the exhaust and also cools the flow entering into the turbo. The length should not exceed approximately 125% of cylinder displacement. You want the exhaust to be as short as possible because you need the heat. The idea is that the exhaust is still expanding when it comes out and you want it to do that inside the turbo, this helps spool things up.

Some turbo books say that it's not the flow that makes the turbine spin, but the kinetic energy in the leading edge of the exhaust pulse, or the shock wave that makes it work. If so, that explains why they want the smaller exhaust pipes to keep the speed of the pulse up. Bigger tubes make volume tanks and will average or slow down that pulse. It makes sense when you think about it and remember, the engine only runs "One" pulse at a time.