What kind of idle do you have. With 20" of vac. it should idle good. unless you have so much timing jacked into it. When you decrease the vac. its probably decreasing the timing and thats what make it run better, 14" of vac. should make it to rich. what does "dont idle good mean"? at first you said it didnt have a loop or lope and its not gonna with 20" of vac.