Welcome to United Bimmer. Since you replaced the intake boot already check all of your vacuum lines. They can cause idle or other issues. Make sure to feel them and bend them because cracks arent always visible. Other options could be your PCV, Idle Control Valve (ICV), or your MAF sensor. Double check all your fuses just to be safe. Sometimes they blow but can still look okay. If this doesn't work check yor starter and electrical connections.