Gsragtop

So I picked up a troubled 2000 f150 today. It runs rough, lacks power, does not idle with The AC on and sometimes stalls. Yes she's a real winner. Lol..

When I got her the IAC was unplugged, and the tube running to the breather was undone an plugged up.. She had 12 codes stored, so I erased them to see what came back. Misfire on 5 and 7 came back with the iac plugged in the code for iac system came back, as did a lean code.

When I plugged the iac in with it still plugged nothing really happened. When I pulled the plug off there was a string vacuum. I'm guessing it was wide open. Motor stalled. Plugged the breather in and restarted and there was a loud whistle, disconnected the hose and unplugged iac. The iac is supposed to be and looks fairly new.

The previous owner said his mechanic said the truck needed a new computer (which I doubt)

Where do I start looking for issues ??