That will be the culprit unless it's one of mine. At least 10 years ago, probably closer to 15 they changed suppliers for those. They have WAY too much spring in them and not enough restriction, so open INSTANTLY and don't dampen the secondaries.
The result is a huge stumble/hesitation/bog going quickly to full throttle.
They also take 12-14" vacuum to apply them (factory spec is 5-6) so don't even do a good job unloading the choke on a cold start.
Here is a link to one that applies at 5" vacuum and restriction installed to set the release time to prevent issues going to full throttle:
https://cliffshighperformance.com/pr...pull-off-67-70
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https://cliffshighperformance.com/
73 Ventura,
SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile),