97 suburban Carbon Build up

I just took off the upper maniford to change a fuel pressure regulator. I noticed a large amount of carbon build up around the first runners to the lower manifold, but not a noticable amount on the second half. Does anybody have an answer or could there be another problem.

Thanks

Steve

10 years old, probably normal, seen this before.

I just resealed the intake manifold on my wife's 99 with only 40K miles on it. It too was covered in black wet carbon up near cylinders 1 -4. If you look, the EGR passage feeds at the front of the intake so it is normal for it to look like that. I used a can of carb cleaner and got it spotless, but it will be back soon.

Pat