Ford Repair: Acceleration flat spot 1965 - 289, edelbrock carb, vacuum gauge

Question
The acceleration of my '65 289 3 speed Mustang is not great.  There is a flat spot at about 15- 20 mph in 1st and again about 30 to 35 mph in 2nd.  I do not have a tach so I don't know the rpm's.  I recently replaced the old 2 barrel with a new Edelbrock carb and intake but the problem is the same as before.  The engine seems to rev fine in neutral and the initial timing is on spec at 6 degrees. Could it be the vacuum advance, if so how do I repair it?  Any other possibilities?  

Answer
Paul,

It could be your vacuum advance. You will need to hook a vacuum gauge to the vacuum advance on the distributor and see if it is to spec. You can not repair a vacuum advance, if the gauge shows that it is bad, you will need to go and purchase a new one to replace the old one on the distributor.
Alot of times those older motors like to run a couple degrees above spec. Try setting your timing forward 2 degrees and see how it runs. Hope that this helps and I am sorry that this reply took so long but I was having technical difficulties by way of my telephone company, which has hopefully been repaired. Good luck.

Ken