Can't bring idle below 1000

[jeff74]

I refreshed a 1996 vortec engine and installed it in my '71. Today was the first time I took it for a good drive, when it's warmed up the idle was around 1000 and wouldn't go any lower with the adjustment screw backed out. Quadrajet 4MV

The carb had a good cleaning and rebuild kit and I put in brass bushings on the primary shaft only, the secondary seemed fine.

I was reading on here for ideas and this is what I've tried so far...

Blocked off the pcv line and brake booster line , no change
Checked the mechanical advance action, it returns to normal on its own. I didn't check the timing.. it was set at 10 or 11 btdc the other day

The other vacuum ports on the carb are plugged, I don't have the vacuum advance hooked up at the moment. I'm going to convert to manual choke , but for now I have the choke linkage held in the hot position.

Anything else before I pull the carb ?

Thanks

This is what she looks like today.