Classic/Antique Car Repair: 74 Dart - Wont idle and dies without giving gas, dart swinger, dodge dart

Question
Hi I'm hoping you can shine some light on my problem.

My 74 Dodge Dart Swinger w/ slant6 starts fine but dies once I take my foot off the gas.  Likewise while I'm driving I have to keep my foot on the gas and brake/shift to neutral to get back home.  It just happened today while I was running errands.  The same exact thing happened about three months ago, but as I was backing out of the driveway to take it to a mechanic it sounded like it was hacking up a lung and then coughed out whatever was causing the hangup.  It ran fine after that.  I took it to the mechanic that day and he replaced the fuel filter saying that was the problem.  I'm guessing he was wrong.

Any ideas?  

Thank you!

Answer
It sounds like it could be the Exhaust Gas recalculation valve (EGR). It is located on the intake manifold near the carburetor. The EGR valve does not open when the engine is cool and at idle. So when the engine warms up the valve begins to open as you add throttle. If it sticks when you take your foot off the gas and does not close then the engine will not idle and will stall. That would be the next thing that I would check. As far as having confidence in the mechanic (?) that jumped to the fuel filter as a cure all, I would say good bye to him.
Brad