<p>Granted, my experience is dated (going on 5 years), but at least back then, Youkoso was an AWFUL textbook, IMO. I’m not sure why anyone would use it, let alone for AP. Genki is okay, as is Kimono (weird name, though), but I’m surprised to hear that you guys use textbooks for AP Japanese to begin with–in advanced Japanese (what is now AP Japanese), my teacher just created her own materials for us to use–I think most textbooks were just a bit kanji and reading comprehension “lite” for her tastes.</p>
<p>OP, you’ll probably do very well on the test with very minimal study, but I think many adcoms may give it lesser weight due to your heritage speaker status. However, other than potentially hurting the curve for non-native/non-heritage speakers, I can’t see it doing any harm for you, specifically, and it could help.</p>