Lots of $ and it still smokes. 94 6.5 turbo. 422K New Vacuum pump, ( it needed it), Black Smoke at Medium Acceleration (BSMA), WG solenoid, (BSMA), rebuilt TC (BSMA), GM ECM, (BSMA). Checked Vacuum again (BSMA)

What am I missing. I replaced the PMD about 6 months and remoted it. Could that be bad again?

Any thoughts would be appreciated.

A puff is normal when you punch it but it should clear up, how much smoke are you talking about?

also it could be you have one of the cross over pipes that looked like mine, I'm not convinced yet that it happened to all of them but mine was pinched almost completely off, this would explain black smoke on the higher rpm scale.
I'll try and find my post with the picture

http://dieselplace.com/forum/showthread.php?t=54179
Check here

Air filter.............

I agree with gmctd, sounds like an air issue. Check your air filter. Also, it is possible that if you have a snorkle in the fender, it may be clogged.

Or collapsed - good thought, TT

This is heavier than normal. Normal for this engine over the past 12 years is for a good puff of dark smoke at hard acceleration. There is also a slight hesitation on acceleration. Could the timing be the problem. New air filter.

I have never had the crossover pipe changed out.

New air filter. There is a slight hesitation on acceleration then black smoke. Over the past 12 years the norm is for dark smoke at heavy acceleraton but not at medium. Maybe I had better look at the x over pipe

New air filter. Original air filter setup. Ther is a hesitation on acceleration then black smoke. Over the past 12 years, the norm has been heavy smoke on heavy acceleration but not on medium acceleration.

Pull the 'snorkle' out of the fender.

Then, if 421,000 miles on the original timing chain set is correct, it is way past due for replacement - anything over a hundred k is past due.

If you find the air intake system is the problem AFE has a new air intake kit for 92-00 6.5L except van which allows a much greater air flow. The design also uses mostly outside cooler air. The air filter is cleanable. Should cost about $299.00 for the system. Make sure it is Pro Guard 7 filter media not Pro Guard 5. I would also check the vacuum harness from the wgs to the vacuum pump and wga.

Thanks for the info guys. I checked the air intake funnel last night. It is clear. Timing chain - hum - never has been replaced. Is it expensive???

Around 350 for GM chain and both sprockets.

The sprockets must be replaced, because chain wear reduces pitch diameter, such that a new chain only will allow enough slack to retard the camshaft.