If you have a friend/shop you know well with a Snap-On or similar scanner to read it, you're not going to get much info. If I remember correctly PSDs aren't OBD compliant, and therefore it is a bit of a crapshoot on what it can see.

My $0.02: No MIL and not running poorly, no problem.

 

They are only partially OBD II compliant (but enough to fall under smog check rules for some states). Many of the codes are not easily read by the generic OBD II software. If you get an SES light (hard code) any OBD II reader can retrieve/clear the code. If you do not get the SES light (soft code) only a reader with specific Ford software can read it.

The easiest examples I can think of are if you delete the AIH or EBPV and don't build/install a "fooler" in the connector to make the truck think it's still there. You will get a soft code (stored code but no SES light) which is not an issue with a smog check. If you don't have the SES light on then their software will not read it or flag you for failure.

If you don't have any issues with the truck then don't worry about it. If you having issues then find someone who has the ford-specific software and see what it shows you.