Cost me a $125 tow bill, and 3 days of the wife not having her car (sorry babe!), but apparently the brass tube that runs in the middle of the venturis can work loose and rotate around. Mine was pointing almost straight up when I discovered it.
It started as a gradual 'accelerates better when you let up on the pedal' per the following quote, but got worse and worse to the point of driving a whopping 10mph down the shoulder of the interstate for 5 miles. lol I initially removed my Hot Spark and went back to points, cause it felt like a dying ignition module (had everything with me to do it on the side of the road).
This took a lot of Googling to come across, so I wanted to share with the group to prevent someone else from possibly throwing money at this wastefully.
To check for this, you can spray carb cleaner down the air corrector, it should shoot out straight down onto the butterfly. I used my leatherman to rotate the tube, and a 3 inch deck screw as a punch to stake it into place. Runs like a top again!
Quote (full link:
http://www.apexspeed.com/forums/showthread.php?t=22373):
3) Lack of power. Well, you used to have more power, and you take your foot off the gas pedal a bit and the car goes faster. Check the auxilliary venturis. The brass tube inside has been known to get loose and start to spin around. take out the venturi, and see if the tube is pointing straight down....So you cant take the venturi out? turn the carburetor over and see if the tube is off centre. If this is the case, the tube from the venturi has taken a little wander into the main body of the carburetor. You have to move the tube to the middle of the venturi and then take it out. You have to stake the edge of the tube or buy a new venturi to correct this issue.