The road congestion only happens in bigger cities such as Tokyo, Osaka, Nagoya etc. I live in a smaller city in a rural area quite far from Tokyo, so there is not much traffic here, although local street is quite small. I can still drive fast whenever I want to though, just have to make sure to watch out for rabbit, goat, skunks etc that might cross the street
Seriously, the boxster has an awesome handling and can do corner in AMAZING speed so it helps.