Why does my car feel sluggish?

Always start with tuning. And tuning always has to start with the timing curve. Initial timing is what you're (OP) is talking about. Well if it doesnt feel sluggish off idle, your intial's fine. But... You have to know the rest of the details on what you currently have. The distributor if it's factory it will have too much centrifical advance, and it will advance too slowly. So regardless of the carb, it will be a pig. So yes, "I don't know" is an answer. But if you are seriously looking for an answer to "why is it sluggish?", and your mind is open to possibilities other than what you might already think is a problem, than "I don't know" isn't good enough. "I'll find out" or "how do I find out" is much further along to finding a solution.

I saw your post when I had written mine - Good on checking. I have several friend who are great guys and have built a ton of cars. But they don't always build cars that work perfectly...lol.
Also - check the throttle lever and your kickdown linkage. Sounds like it's not adjusted properly... Prob because of the intake you have.