If the throttle shaft is worn bad enough, you may see gas puddles on the intake on either side of the carb. This is not an uncommon problem. Especially since you said it picks up when you spray it with carb cleaner. Here's a good fix if this is the trouble!

500 Holley 2 barrel perf carb carburetor 4412 Reman Bright Zinc Finish | eBay

There are tons of these things available.