Looks like that weird after cooler set up that I believe only EARLY efi 4.9's have. It was supposed to run after the truck was off to keep the fuel from boiling off or something like that. My 91 does not have it.

 

You appear to be correct. This tube is the Fuel Injection Cooling Rail, and a fan connects to the end of it. From what I see most people have gone without using it and have had no problems. Thanks you Krisverde for your assistance.

 

Please tell me you didn't put that throttle body spacer on...

 

Hehe this isn't my truck. I pulled this pic from another post for reference, I do not recall who owned the picture.

 

Well I started the gal up this morning to a sluggish idle that would fluctuate up and down until she finally would die out. Pulled the vacuum from the MAP and held my thumb over it to a smooth running truck. Switched out the map and she is back to running like a champ. My issue now is the Fuel gauge pegged beyond full. I have been trying to test the selector switch, but not sure I am doing it right. I read "Go to the switch and make sure there is voltage on the Yellow/White wire. When unplugged the gauge should peg full, and if the wire is grounded, the gauge should peg empty. If the gauge goes full unplugged, try jumpering across the plug to connector Yellow/White (Y/W) wire to each sensor wire. If the gauge reads normal, replace the selector switch. If not, follow each wire to the sender to see where they are shorted. Cut and run new wire as needed." somewhere, but not sure I understand the jumpering across plug part. Any help is appreciated.