1970 Mercury Cougar Acceleration Issue

Engine Mechanical problem
1970 Mercury Cougar V8 Automatic 25000 miles

When accelerating between 0-35 mph, my Cougar makes a loud noise that sounds like “sucking air through a pipe". You can really feel her struggling. Once it hits 35 mph, it jerks a little and runs a smooth as ever. I just had a mechanic adjust the timing and carburetor. They also replaced the intake gasket. My car had the same issue previous to the adjustments, except it would cut off around 10 mph. I would say we’re making some progress, but I can’t seem to figure out why she is making this noise and struggling so much. Could it be the tranny?