getting back on the road after sitting long time

[doodah man]

So I have neglected my truck for a while now. I guess it's probably sat for over a year with a dead battery and I wasn't driving it regular before that. I need to put my other truck in the shop so I picked up a new battery and poured some high octane gas in the tank on top of the old gas (no stabil in there).

Turned the key and it started up with only a couple pumps of the gas pedal. I'm feeling pretty good so I let it warm up a little bit. Turn it off. Crank again. Fires right up. Try again no problem. It's idling beautifully. Just like old times.

It needs some tranmission fluid, so I kill it and take the other truck to the parts house. Get back. Fill the tranny and crank again. Starts perfectly.

Pull it up front of the house and fill the tires while letting it idle. Get my son to go for a little test drive. I test the brakes at the end of driveway and they feel a little weak, so I back up and give it so gas and hit the brakes hard. Then the engine dies. I try starting again and it wont fire until I pump a bunch of gas in there. It starts up but it will only run with the gas pedal down. I start it a couple more times but it's the same. Very rough and only if I keep on the gas. If I let off, it dies right away.

Anything obvious other than bad gas? It's got HEI ignition. Thanks!