This might've been suggested before in another of your threads, but perhaps your overrun shutoff switch is sticking. It's the switch that's activated when the throttle is completely released, and will limit the amount of fuel you're getting like you say.
Put a meter on it and test it's output as you switch it if you can. I believe it gives infinite resistance and no resistance, or therabouts.
Only takes 5 minutes to do, and nice to know if it's working - it helps fuel consumption.
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black