Car is almost good to go

[fighterm]

Over the past month after purchasing my e36 m3 I did a cooling system overhaul and recently a suspension overhaul. It is almost good to go, some minor issues such as BLC on OBC occasionally, but brake lights still work. Need a few minor parts for the car. One thing... after new suspension I get new rattles around the center to rear of car, car squeaks a little which I attribute it to stiffer suspension, but loose plastic rattle noises have been amplified. If noise is coming from the middle of the car should I be concerned for the transmission mounts? Or could it be I am hearing back seats rattling? Sounds more like plastic rattle... should I be concerned? Btw the car has 82k miles. Thanks.

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Edit: No insights?