ORIGINAL: Charlie P.
In addition to the "leaning in the air" noted above there is another factor that has nothing to do with the engine at all.
Sound travels at 600 fps +/-. If you're 300 ft away that's a half second delay before you hear the difference whan you make a throttle change; 600 ft away = 1 second delay, etc. It can be quite noticable.
That's one of the advantages of four srokes. You can see the puff of smoke when you hit the throttle. That puff indicates right away that you have throttled up, even if it is a couple seconds before the sound gets to you. Cloudy days are a problem though as it is hard to see the smoke.
Don