wmburns, I solved the 4011 on my 97 Cobra today. Been putting it off dreading dealing with another emissions CEL. And there is shockingly little info on this part of the system/this DTC 4011, on the internet. But I found a lot of people asking how to fix it. I swear I've learned more about emissions systems on this car than I did on my 93 LX...
In fact I bet I spent less than an hour figuring it out. Mine was the vacuum solenoid. I googled the Ford part number on the solenoid and the Dorman part #600-400 came up. $20 at Advance Auto Parts on the shelf. Awesome. Exact match.
I guess mine seized up. No vent to atmosphere on the top port and no vent between ports with 12v applied. Had good vacuum at the bottom port and no vacuum on the top port 10 sec after initial startup. So that was that. Easy fix.
I also had to isolate the purge canister flow sensor a few months ago. Replaced the solenoid anyway as well for gp.
I ordered the Ford emissions shop manual off Ebay. Priceless.