Ford Repair: 86 Ford F150...fuel delivery/exhaust problem??, vacuum leaks, leaky injector

Question
I have an 86 F150, Auto 302,FI,(not original motor). The other day I was driving along and the truck started to sputter and died out. The truck will restart all day long but will not stay running unless you keep your foot on the gas. I ended up driving home like this, revving up at stops. There was obviously a strong gas smell and a black/blue smoke coming from the exhaust. A couple months back I replaced the coil and advanced the timing just a little. The truck had been running well up until this point. I have checked the fuel pressure...35 pounds but starts losing pressure at about 1 minute.(not sure if thats normal) I pulled the vacuum on the regulator, no fuel present.I changed the plugs to see what they looked like and it needed to be done anyways. They were pretty carboned up. The only other thing I noticed is that there is a return? line from the exhaust running up near the firewall, T's off and runs to the old air pump?? I assume the air pump is operated by the ac in front of it which has never had a belt on it since i have owned it, so i assume the air pump does not work.Not sure where the other one goes.
Here are some of the things I have been told by various people that could be wrong (none of which are mechanics!)
Leaky injector(s)
Plugged muffler/converter
The return line that broke is the problem.
Any ideas are greatly appreciated!!!
Thanks in advance,
Shawn

Answer
The fuel pressure on your vehicle should hold for longer than one minute. Usually enough pressure will hold overnight to prime the injectors speedily. If you are getting black smoke this is an indication of way too much fuel, as is the carbon on the spark plugs. If the regulator is not leaking, you may have to check the injectors for one stuck open or leaking. Also check for any vacuum leaks, these can drive the oxygen sensor lean and enrich the mixture