I've had this problem off and on since I installed the new Edelbrock. In general, it runs really well, nice pick up, good cruising, etc. Unfortunately, about half the time it runs pig rich. It idles like crap and tries to stall. The exhaust smell will knock you down. It's just ghastly. I called Edelbrock's tech help line a few times and found them to be, shall we say, less than helpful.
As you can see, I've backed off the choke as far as I can. The white mark on the black plastic case is way off the lean scale.

Funny that even with the choke so lean and the engine at operating temp, the choke plate still has this much play.

That's not me pushing the plate over. There's that much slop in it.
Turning to the other side, I see this.

The fast idle linkage is stuck on the adjusting screw. If I back off the screw just a hair, it doesn't hang up anymore. The problem is solved. It came from Edelbrock hanging up like this. That's poor QC, if you ask me. It's worse that Edelbrock's tech help line couldn't help me with this and could only be surly and rude. Anyway, if you're having trouble with your Edelbrock running rich off and on, check this out.