Idle mixture screws not working

[mother$hip89]

I turn the idle mixture screws and they don't seem to do anything. Could this be because the car is idling around 1000 rpm. If so, does anyone have any ideas why the fast idle can't go below 1000 rpm and keep the engine running steady.

[Frank400]

You're probably on fast idle (choke on) and/or there's a vacuum leak and that incoming air is making it run that fast.

   What is the carb number, what's it sitting on and is the engine stock or modified, and what was done to the carb ?

[mother$hip89]

I tried smoke and carb cleaner and couldn't find a leak (I did find that carb cleaner makes the engine slow down instead of speed up for some reason). the carb is 17057253 on a 1974 Oldsmobile 350 that I do not believe is modified. The carb has been cleaned and rebuilt and has single taper 0.048 rods.

[mother$hip89]

I've made another discovery. The O2 sensor is at around 0.9v, which I was told means the car is running rich

[mother$hip89]

Oh, I completely forgot to mention, the idling issue is only in park, in gear it can go down to around 700 rpm.