A 4160 is Holley's vac carb...600cfm but they also have a 750 under the same #. Something is weird obviously. Why did you disconnect the exhaust? Was it running fine before? If so you probably knocked off a vac line or ironically something went awry. I had a 4160 on my old Nova and was constantly having problems with it. Vowed never to own one again but it was just that particular carb that had major float problems.
Nick
1994 22' Classic-454 B1 Red & white
1981 13' Whaler sport(original owner)
South Tampa Bay, FL "May I mamoo dogface to the banana patch?"