having a surging issue at idle where the revs bounce between roughly 400rpm and 700rpm in a 2-3 second interval. i'm thinking possibly an old vacuum line somewhere, but is this an issue that others have seen in the past and know about? i'm somewhat new to 500s, but not german cars in general. i took a video with my phone, but it's too big to upload. i'll have to work on downsampling that vid and posting it. any thoughts would be greatly appreciated. thanks!