Cylinder miss. I can’t figure it out.
 

I have a 02 sonata 2.7L v-6.
the car just had the heads completely rebuilt, new timing belt and all. When the car first starts it has a bit of a rough idle then soon after becomes a miss, the miss is on cylinder 5 and 6 but was told it first started at 2 and 3. Cylinder 5 miss goes and comes I get cylinder 6 every time. While driving the car for about 45 mins it has power after that it falls flat and no power.
I’ve moved cylinder 6 plug to 4 still miss on 6. I moved the injector and still on cylinder 6. I removed the exhaust and looking into the cats the front one was clean. The back cat was glowing red inside.
Any help would be greatly appreciated!

The glowing red is due to the converter attempting to clean up a very rich exhaust.

The first thing I would suggest is a compression check so we know if the timing is on the money.

So I ran a quick compression test on the front 3 cylinders and I got 60 psi on 2, 50 psi on 4 and, 55 psi on cylinder 6. I’m gonna pull the timing covers off and verify timing.