I had a lot of issues with my Holley carb and the reason was the previous owner monkeyed around with it. Running rich. Fuel starvation. Gas smell. I have a 4150 870cfm and it sits atop a Roush 427r with 550hp. I even checked with Roush to confirm it as the correct carb for that engine. I looked at quite a few videos on YouTube about tuning Holley's. I fixed it by taking it apart, cleaning it, rebuilding it and returning it back to factory specs. All the wrong parts were in it. I found 3 things critical. Correct jets. Correct power valves and correct float settings with new needle and seats. The floats are a little tricky to get right. Too low...fuel starvation...Too high...they leak and you run very rich. Fuel pressure is critical on Holleys. They do not like too much pressure. Holley's can be touchy. Correct size power valves are very important when delivering fuel at wide open throttle. The thing runs like a top now.
Good luck
Here is the data for mine which is probably very close to yours.
Fred