The undercovers are probably just that, "aerodynamic" undertrays covering those various pieces. Under tank probably refers to the fuel tank. Japanese usage of automotive terms is sometimes hard to decipher (even for some Japanese!) because they are doing a conversion of the English into katakana (un-da tanku!). Took me a while to figure out what they were calling indicator...j
Regards,
Paul Hansen
www.avoturboworld.com
www.facebook.com/avoturboworld