I am not going to disclose the exact part that is damaged so you can have the fun of doing that yourself. I have 4 levels:

LEVEL 0: [NO EFFORT] Satsuma runs (you will need to install muffler to get it to pass inspection)
LEVEL 1: [EASY] things that degrade when cars sit (hint: you might have to charge on of them)
LEVEL 2: [NORMAL] things that would break after use and time sitting (freebie: Waterpump)
LEVEL 3: [HARD] things that would need to be replaced after 250k Miles (freebie: Fuel pump)

So enjoy! (Hint: check the notebook at kitchen table)