Number 4 cylinder running hot!

You can get black dry sooty plugs after idling too much, but when you fly or run the engine at higher rpm’s that burns off. Cooling the outside cyl. Will only help reduce the CHT and not so much for the EGT. 
Something to try go fly a short around the pattern with no air filters. EGT’s show fuel burn inside the cylinder and are affected by air intake and fuel as a general rule. The air intake can easily affect the EGT’s. One step at a time like Sean says. Also try swapping another EGT probe for the hot one and see if it’s the same.

Today's update.
1.  The vacuum/draft duct did nothing.

2.  Removing the air filter was very interesting.  I removed air filter for 2/4 side.  On climb out the EGTs dropped a lot. Once I leveled off though it did not have an impact on EGT and #4 shot up into the red.  Yawing as much as I could would slowly bring it back into the yellow.   Take a look at the attached pics.  The air filters are pretty simple and just a simple K&N mesh.  I guess the tumbling air around the seat just kills any predictability.

3. Until the intake o-rings show up I tried some RTV sealant around the manifold contact point.  That did nothing.  So the o-rings will most likely not change anything.

4. Again, when you look at how out in the open the engine really is, why is #3 and #4 more than 100F hotter.  Event when just sitting at 2500 in my garage?  

Something is going on with 3 and 4 and I don't know what.   And my other Rotax Owner topic about the mag 1000 rpm drop could be related.  I believe that I will take the chance replace the trigger pickups and harness.  I hope that I'm not wasting my money on it.

Oh, and I will swap out the  EGT probe now even though when idling I can clearly see that #4 is hotter than #3 when using a temp gun. by at least a 100F.  Also, the CHT's (water temp sensors) and oil temp is quite low so I don't think that the oil cooler and radiator are undersized.

The dash pics are of a MGL's Max numbers during the last flight.

Thanks.

Is this issue something new? Was any Maint. Performed just before this happened? You EGT’s seem to be hotter than most. Have you checked with MGL to see if the temp readings in the cockpit may be instrument related? I don’t personally know, but some readings for our instruments require a resistor in line?

Just trying to narrow down the possibilities.

I hear you on that.  The engine had 450 hours on it when I purchased it.  The MGL and all of the EGT sensors are new.  MGLs do take some tinkering to read correct and to read steadily.   Being that the vacuum duct idea did not work at all I'm wondering why #1 and #2 run evenly and so much cooler.  Even when running in my garage.

Thanks!

Here might be something.  I found this ref in the Heavy manual, 74-00-00 page 19.

Trigger Coil Assignation on 912 series:
Trigger Coil A3/4 serves bottom plugs of cylinder 3 and 4. While Trigger Coil B3/4 serves the top plugs of cylinder 3 and 4.

#3 and #4 are my two hot cylinders and I have a big rpm mag check issue.    Since I will be guessing and replacing the trigger harness I may stomp out both issues?