You've already heard enough about the virtues of the Qjet. You've also heard that the intake you have isn't the best for a street engine. I would start there. You don't want an open plenum intake on a street engine, especially a mild one. You are losing much low end torque and response. If that is the issue you're dealing with, find a performer or similar dual plane intake to try. If you're convinced to ditch the Carter, I second, third, fifth, whatever, endorse the Edelbrock over a Holley. Holley has name recognition with racers and that is about all they are good for. They are finicky on a street engine and can work fine in the temp/humidity conditions of one day and run like crap the next when the weather changes. I was a die-hard Holley man for many years until I bought a Camaro with a 600 vacuum secondary on a 350. The carb just plain works on any day I chose to drive the car. No fuss, no screwing around. As for mechanical secondaries, they are for manual trans cars. You want the vacuum for an automatic. Mechanical carbs will hesitate, or bog, horribly when you mash the throttle at low rpm, because everything opens instantly. The vacuum drops to near zero and the intake is flooded with raw fuel. Not the best formula for performance. Unless you like playing with the throttle to keep the engine running cold, the electric choke is a must also.
As for the Cater, if you have run oxygenated fuel in the past, the carb is full of corn residue. It needs to be completely disassembled, soaked and cleaned properly. Only use non-oxy fuel in a carburator. They were never built for the toxic environment of alchohol. Do a web search for pics of aluminum body carbs that have been destroyed by corn based fuel when allowed to sit over the winter. It's shocking to see what that crap will do.