93 F-150 engine stalls - koer code 311

My f-150 has 150000 miles and recently started stalling when first started it acts flooded untill I rev it up hard then comes out of it. Some days it will stall at every stop then run fine for up to a week. I ran the codes and 311 air system not functioning came up.
the air pump was noisy so I replaced it. The problem hasen't changed and the code is still there. Could it be the air bypass valve and would this cause the stalling?