wont stay running...again

1 more vote for vacuum leak.

I'm having a identical problem with a rebuilt slant. I sprayed some carb cleaner around the intake, and the engine steadies out, which tells me I've got a vacuum leak. While in park or neutral, it will run decent but not great. (Idle quite a bit higher than I'd like though) But in gear, it sputters for a second or 2 and then dies unless I'm pressing down on the gas.