My point isn't that it was or was not a problem, my point is that it probably wasn't more of a problem for the Me-109 than for other planes. We know that taking off and landing was more of a problem for the Messerschmitt than for most fighters, because references to it are found in abundance. So if the exhaust was more of a problem for the 109 than for other ships, one would expect references to it to likewise abound.
Of course I have no data whatsoever, so I'm not saying that it was or was not a problem. I'm just pointing out that there's been no data presented to indicate that the Me Hundertneun was more prone to having smoke or fumes in the cockpit than any other kite.