No expert on tuning, but while perusing tuning threads I had read about similar symptoms coming from either a faulty or misconnected MAF sensor. Check that, maybe?
Edit: What also leads me to this conclusion is it sounds symptomatic of a fuel/air mixture imbalance. Your car is running under it's own power while the clutch is forcing the engine to turn over, but when you push in the clutch and separate the wheels from the engine, it cannot keep itself running. You also mentioned that stutter at cruising speeds.
"So, a dog over-steers, which is more fun than an under-steering Hyena so... you want a Mazda MX-5 because it's rear-wheel drive!"