340 No low end power

I fought this issue with my Cuda and I knew (or thought I knew) everything about the car. My 340 ran great at full throttle, but had no low end and poor vacuum and idle. Found a very leaky intake. Older Edelbrock manifolds may not be properly machined leaving a gap at the bottom of the intake. Symtoms: low vacuum, poor idle, inability to set A/F ratio, idle screws out excessively (4 turns or more), no sensitivity to tuning.. This resulted in burnt valves and further loss of power.
I started with a compression test which showed low cylinder pressure in #7. A leak down test (using a home built gauge set) showed other problems in other cylinders. Took heads off and replaced manifold with Air Gap. Idle problem solved, and picked up 1.2 seconds at Brandimere.
So, check everything. Know your advance curve and set points. Verify the cam instillation via centerline measurement against cam specs. Know the stall speed of the converter, gear ratio, tire size. Use on-line programs to correlate ET and MPH with HP. Compare your results to best theoretical and look for reasons why your car may not be performing.
Engines are not mysterious. There is always a reason why things happen. It just may be a pain to find the root cause, but it is there.
Best of luck,
Bob