Aphelion

If I run the car through 1st and 2nd really fast, then I disengage the clutch and let off the gas (right after I've hit 6 or 7k in 2nd), it normally dies. I don't hear any weird noises, but when I let off the RPMs it falls to around 500 RPMs and then shuts off. When it doesn't do this, the RPMs fall to around 600 or so and then bounce back up immediately. It happens in other gears, but it's not as frequent - it seems like I have to rev it quickly and then let off the gas completely to make it happen, and in 4th and 5th gear, I can't rev quickly enough to make it happen. I'm wondering if my lightened flywheel has anything to do with this, and what I can do to fix the problem.