Could be anything from valve train issue, to fuel lean, to ignition issues. You did a compression test, but this can mask some issues like tight or leaky valves. Second thing would be to perform a leak down test on all cylinders. If both tests come out clean, check ignition system for issues, timing order as Jeff mentioned. Is the ignition electronic? Points? Having a vehicle carb is a safety issue, but it would run ok on one. You could have a vacuum leak on one or more cylinders that can cause this condition. I use carb cleaner while running to find these leaks, the condition will clear when the leak sucks in the cleaner.