So I just finished my B20 swap and finally started it up today. Its got a real jumpy idle, like it idles around 500-700 RPM (which seems real low to me). So, I decided to drive it and while driving it cut off on me 2 times. I also have a real nasty exhaust leak. What are some of the reason the idle would jump around so much?

Also, I never really noticed this before, but when my front wheels are off the ground and the car is in neutral the wheels still spin. Is this normal? (the B20 was an auto. but my coupe is a manual.