I spent the last few days working on my 171 and 174 problems. Tried going to the dealer for some advice, they "didn't trust the autozone codes" and would need to have a technician work on the car. I said thanks but no thanks.
I was sure it wasn't the PCV vaccum leak as I pulled the PCV valve and felt plenty of suck on it while the truck was running (97 F150 with 120K miles). I thought about the fuel filter thread but pulled the records from the last service a year ago and found I had the presence of mind to have it replaced. So I stopped myself on that. I really didn't want to spend the money on O2 sensors, so I tried the Mass Air Sensor by pulling the air filter housing and putting my finger over the hole where the sensor was, the trucks idle changed so i figured it was working.
Not beated down yet so I went back and read more threads and decided to go back to the rubber elbow from the PCV. I pulled the valve again, found lots of suck, and then followed the line (expecting it to lead to the rear of the intake manifold) and found it attached at the front of the manifold, under the main intake, in a horrible spot to work on. The elbow was bad, had an "eraser sized" hole it it.
Went back to auto zone, put something together with hoses and such, had my daughter (it is her truck and she has much smaller hands) put the thing together....went back to autozone, cleared the codes (free) and drove around for a half of an hour, no come backy....the codes I mean.

Thanks a lot for the help

john