Here we go:

1) pull oil filler cap and have some blow by. not enough to push hand up of filler tube. No signs of oil or radiator fluid consumption. What gives? Do I need to replace the CDR? Truck has almost 300,000 and no real records of maintainence prior to me.

2) During christmas trip vacuum gauge went to zero. Check codes and got 78-wastegate error code. Vacuum now only reads 15. When start to rev engine it will go to 20, but when hit about 1800 rpms cuts out to 15 or less. Vacuum is suppose to be at 25 no? All vacuum hoses new. New wastegate soleniod. Armatuer on wastegate control is stiff and unmovable with vacuum hooked up and truck idleing. Is this sign of my vacuum pump going?(almost 300,00)

CDR is a normal maintenance item. I think it's good for 60k miles but if a lot or oil is getting to it that may be a factor.

Is vac dropping when the turbo kicks in?

Where is the tap for your gage?

WG should read 15", but vacuum pump should read 25" or better at idle and should not drop at any rpm

Checked the vacuum pump: only registering 15 at idle, then varies with rpm, will go to 20, but after about 1800rmps goes to 10 or less: This is at the vacuum pump with nothing hooked up. So I believe the vacuum pump is going south.

If the CDR is plugged would that cause some blow by? I am just concerned maybe something internal is going on that I don't see or can diagnose. Again, there is no coolant loss, it is as full as the day I updated the cooling system. No signs of coolant in oil either. Only uses about 1/2 quart after trips of 5 hours or more pulling my trailer up and down hills. No Idea on this one.

Not much experience with the CDR other than just changing it for no apparent reason. It lets the pressure off of the crankcase using the turbo intake without allowing excessive vacuum from the turbo. Sort of an active venting system.

Normally if you were to remove it all together you should not have any pressure coming out that would be noticeable. Such as through the valve cover, dipstick tube, or oil fill tube.

Blowby is normal, moreso when engine is at 190deg operating temps, moreso as mileage increases.

Also, engine oil lubricates the turbine shaft, with it's elevated temps, which results in even more hot-oil fumes.

If blowby is not puffing back thru the filler tube, it is not a problem, other than your engine is very high-mileage.

At 300kmi, you should seriously consider replacing the timing chainset, as well as the injectors and Inj Pump - you would be pleasantly surprised at the difference in driveability.