Something isn't right..

I don’t trust timing by ear except for maybe idle. What advance stop bushing is in the MSD distributor? Likely you have too much mechanical advance if you timed it by ear at idle and it has anything but the black bushing. And even then it might be too much if you’re above 18 or so initial. I would do two things before anything else. SET the timing where it needs to be. Something like 18-34. Then leave it there. Next I would verify rotor phasing and if it’s off correct it. MSD makes an adjustable rotor for that. It works awesome. Then, and only then work on the carb tune.