5.7 Timing Troubles

Looking for some advice into setting up the timing on my 5.7. I've been fighting a nasty cut and bog on full throttle hits ever since I got the engine in the car. At first I thought it may have been a carb problem, but I tried all the accelerator pump settings and some different step up springs (it's a Carter Comp AFB 625 cfm) with no noticeable change at all. Before dumping the money into a new carb I figured I'd try to mess with the timing and see if it made a difference. I'm running the MSD 6 Hemi timing box with an Indy Mod Man single plane intake. I'm running the stock MAP sensor that came with the engine when I got it.

I hooked up my laptop to watch the values real time (rpm, degrees of timing, and MAP sensor) and at cruise I'm running between 5 and 6 psi (absolute pressure, so around 10-12 in Hg vacuum if my conversion is correct), and on a full throttle hit I was getting around 12.6 psi. The stock MSD timing curves have a mechanical advance that builds to around 26 degrees of timing or so around 3000 I think and then a slight taper after that. The vacuum curve starts at 10 degrees up to 6 psi and from there it starts cutting the timing and even goes so far as to go negative around 10 psi. That being said, on a full throttle hit the car was losing 17 degrees of timing on the stock map, which I figured may have something to do with the cut and bog. I changed it so that it would just cut to zero (like a normal vacuum advance) at 12.5 psi, and the full throttle issue seemed to go away. However, a few hours later I took the car out again to cruise a bit, but the issue is back.

Long story short, is anyone out there running a carb setup with the MSD box that has had similar issues? Any advice on what I might try to do to fix the problem? I tried unplugging the MAP sensor entirely to remove the vacuum advance and it seemed to fix the problem, so I'm fairly sure the issue is in the timing curve, but I'm not sure how to go about fixing it. I cut the vacuum advance by around 4 degrees across the board and upped the mechanical curve by 2 degrees to keep roughly the same overall timing and the car feels like a rocket now with the extra mechanical timing, but I don't know how far I want to push it on plain gas since I want to keep street drivability.