77 KZ400 runs rough when throttle opened

I had those same mufflers on my 400 and they were gawd awful. I replaced them with some MAC skip-ons.

Ok so we adjusted the valves this morning then put the carbs back to the stock idle spec per the owners manual. It still has the same issue. It does idle slightly better. I looked at the timing advancer and could see it seem to expand when i rev the engine. I did not take off the points plate yet. The diaphragms were changed yesterday with some brand new ones from kawasaki. Anything else I should try? Is it possible my coil is going bad? Or maybe I need to readjust the points and timing? Or should I skip that and go straight to a compression test? Also I was looking at those mac mufflers or some emgo mufflers. They don't seem too bad for the price.

Is it possible my coil is going bad? Or maybe I need to readjust the points and timing?

Those seem like reasonable culprits.

I just decided to do a compression test before I keep spending money on parts. The right side came out to 125. The left side was 140. I believe that is just over 10% if I did the math correctly in my head. However, I did not put any oil in the cylinder yet to see if that raised it to check to see if it was the rings. Do you all think this would be enough to cause the problem it is having?

That is more variance in compression than you would like to see, but that will not cause the problem you are having.Have you checked to see that you are getting good spark? You can remove the plugs, then stick them back in the boots with the threaded part of the plug on the engine so it can ground, away from the spark plug hole. Turn on the key and hit the starter. You should see a fat, blue spark from each plug. If the spark is weak and yellow, you are not getting enough power to the plugs. If the boots and secondary wires are really old, they may be broken inside, or the insulation may be badly cracked, both of which will prevent good spark. The boots are easy to replace. If you do, avoid resistor boots. Sometimes the ends of the wires where they go into the coil can be bad. You should be able to remove the wires (typically there is a threaded cap holding them in) and cut off about 1/4 inch and reinstall. If the wires are molded in, you are stuck with them.

agreeing with Texas, and adding;
check that you have good fuel flow. Rust from the tank could be choking fuel supply.

Change the point, plugs, and condenser You have to do that just to rule them out.

Here is an update. I checked the spark here is what it looks like. Looks kind of weak to me... Here is a video of it and a picture of the coil I have. What would you guys suggest for me to do next? Thanks!