So, my car was out of commission for just over 2 months because I blew my head gasket. Don't ask why it took so long...Anyway, I got it back about a week ago with pretty much everything new in it. Gaskets, bearings, belts, spark plugs and wires, the works. I also had an injen air intake put into it and a stage 4 clutch. My issue is that when I'm going about 20 mph there's a weird vibration/rubbing sound that comes from my engine. It has a pretty bad rattle when I don't get the car moving properly as well.

So many problems. Continuing on, when I engage the clutch the RPM drops to between 500-600, and it occasionally dies. but when the clutch is out it sets at between 750-800. Also, the clutch engages super fast but I've determined that that is just because of the type of clutch it is and I need to get used to it.

Any ideas on what could be causing any one of my numerous issues?