advance stuck?

I think I know what my problem is, but, wanted to get other opinions. I was having carb problems (I thought) so I switched to a spare weber. As it turns out, that was not the case. The car starts and runs great, actually gets better mpg than the original carb, but, when you accelerate hard, such as passing, or on a entrance ramp, the motor wnts to go, but, it's like an invisible hand holding me back. If I back off the throttle just a bit, it picks up a little, but, not much. I think this is the advance weights not doing their job. Am I correct?
Gene