599 diagnostic help please

[TeXpress]

After my 1995 k2500 smashed up its ds4, I swapped in a db2 off the truck that donated my current engine. It ran fine for a few months, and suddenly developed a miss/rough idle. I put new injectors in it with no change. Found a fuel supply line leak and fixed it which makes it feel more rough and less misfire.
The weird stuff is that it rolls white smoke with anything less than full advance, which brings the smoke to a steady haze. There is also a weird whuffing sound from the right bank which might be an exhaust leak between the turbo and downpipe. Is there supposed to be some kind of gasket there?
Right now I'm thinking either the pump is dead or the timing chain stretched or jumped a tooth. Any thoughts?

 

[3500GMC]

First thought is valvetrain.. Maybe a broken rocker button?

 

[6.5L]

or a blown headgasket if it is making a whoosh from the right bank and smoking white. That's my thoughts. Don't need high boost to blow a headgasket. Our other 6.5L, which has maybe seen 5psi tops, blew it's headgasket a few weeks ago.

 

[Will L.]

It sounds funny but, smell the smoke. Diesel smell or sweet antifreeze.

 

[TeXpress]

I'm almost positive the weird noise is from the downpipe leaking, so it might have just a rough run condition. Exhaust smoke smells like diesel, no coolant. I started taking it apart this week, and I'm thinking about having the localish diesel shop take a look at the pump. Does anybody know a way to check crank to cam timing with the timing cover on?

 

[3500GMC]

Unless installed wrong, the cam will be in phase with the crank or until something breaks. Chains can get Real loose to the point of poor perf but rarely if ever 'skip' without something going very bad.

 

[TeXpress]

Thanks, it should be okay, then. The chain has only been on for ~5k miles. I was looking at some of the videos people have put up here of trucks with worn out pumps, and they look and sound exactly the same as mine. Unfortunately, I just bought a nv4500 a few days ago, so I'm poor as dump. I'll be taking the pump to the shop within a couple weeks though.