Slant won't drive over 25mph without cutting out

Just to throw out an update. It now runs full speed after changing the plug wires. Must have been too much resistance in one of them. They all look fine visually. Might put an ohm meter on them and see if there's anything noticeable there.

The vacuum is still low so it seems like I have having two separate problems. Still haven't figured this one out yet. Going to spray soapy water on the engine and push some air into the system and see if I can find any bubbling. The carb cleaner is telling me the only leak is at the throttle shaft bushing but I suspect there's another leak somewhere that I just couldn't find with that method.

As always, I appreciate it anytime you guys take time out of your day to give advice.