I have an 04 is300 and I have not been able to figure out the reason behind this. For some reason I’m idling super low (around 350) in drive. Sometimes it goes that low in park as well but usually it goes back up and will just drop back down when I put it in drive again. When it gets that low my car starts noticeably vibrating and gets a little loud. However, if I put it in neutral it shoots right back up to around 700 and feel/sounds great. It used to also go back up when I turned my AC on but that is no longer the case (note: I haven’t had cold air in years). I also don’t have any dash lights or codes popping up. I don’t think it’s a vacuum leak because it’s consistent once it gets down to around 300. I’ve changed my coil packs and spark plugs, cleaned out the throttle body, and cleaned the maf sensor. There are potentially other things but I’m blanking lol. Any thoughts or solutions anyone can offer?