One idea that I had last night(actually, it was this morning) on my long drive home at two in the morning was setting something up so that users could go through a list which would have all the parts in the parts database, and then they could check which parts they have on their car, and give a rating of the part, how much it costed them, how much installation costed, etc.
This way, potential buyers could come across a part in the database and find ratings of the part, as well as prices and estimated installation costs. There could even be a link that's something along the lines of "Click here to find all members who have this part." >

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The only thing that kinda worries me, is I'm not sure if many users would want to go through a long list and fill in information, and if only a couple people used this feature, it wouldn't be very helpful. What would you guys think of a feature like that?