"There's no free lunch, unless you could move the engine forward to the point that a short-primary merged header with a long collector and the attendant exhaust bend would fit under the apron. An IM comes close, but not enough." originally posted by Stan Galat
Stan is right. I have a Sebring-ish exhaust on my Spyder. Mid-engine placement allows extra room for the exhaust. Mine works well, but I've never measured the lengths. I do know that my motor was dyno'ed and jetted with the exhaust I have on the car. You should see Lenny's Tangerine Racing custom-made on his type4 Spyder. It is pretty damn good.