Car shakes under 1200rpm

[cmat1120]

So i have an sr20det and when the rpm's drop below 1200 the whole car shakes. I also can't get the car to idle under 1000. I think vacuum could be the culprit for the high idle(boost guage is showing less than 10 psi of vaccum at idle), but I can't figure out why it shakes so much. It doesn't feel like it's going to stall, but rather just makes the whole chassis vibrate. It immediately goes away once i rev it up past 1200 rpm though. One thing is that the car does have an aem fic and I believe it to be improperly tuned for the current setup and idk if that could cause anything(maybe improperly setup ignition timing?). If anyone knows of any solutions or anything to test I would appreciate it. Thanks.