Mystery holes in type4 head

[Pete S.]

I, recently, cleaned up some decent type4 heads. I noticed that three of the exhaust ports had an additional hole in them near the valve guide. They seem to exit towards the outside near the intake port. From there, they go all the way through to near the guide(exhaust port side). What are they for. Weird thing is, on one head there are two of these holes and on the other head there is only one. I have another set of 1800cc type4 heads that do not have these holes. What's going on here?
Any insight appreciated.

Pete S.

[ViolentBlue]

later model EGR system?

[Pete S.]

Why only three of the four exhaust ports?

Pete S.

[Patrick]

They definitely sound like EGR spouts, though the head with only one has got me stumped. Can you tell if it was possibly welded up? The only hole I can think of that would be one-per-head is the cylinder head temp sender but that one doesn't go all the way through.

[Pete S.]

After looking at them closely, I don't believe that one of them was welded. After talking with my shop instructor about this, he suggested that I find a shop that does good aluminum welding and have them welded shut.
Still baffled!
Thanks for the input

Pete S.

[Pete S.]

I talked with a VW mechanic and he told me that the late model 1800cc busses with carburation had an airpump with hoses attached for emissions purposes. And yes, only three cylinders had these holes.
I got them welded up for use on my 2ltr.

Pete S.

[Patrick]

Did he say why one cylinder was excluded from the air pump?

[Pete S.]

He did not know why. I would imagine that one of the cylinders ran normally hotter than the others. Sorta like the #3 cylinder in the type1. Enough heat burns enough fuel and no additional clean air is needed for emissions(?).

Pete S.