FLYINBRIAN - Like I said... probably a stupid question... I have a buddy thaat bought a used Chevy.... pinged like a Bas&^%$ ONLY under tow.... ran great(for a chevy).... otherwise... he chased that ping to hell & back.... finally found it had an aftermarket chip from the previous owner.... put the stock chip back in.... ping gone! ya never no;)

Have changed several of the intake gaskets at my shop. Seems to happen quite often on the 5.9 V-8.

You have all the syptoms too.

So how much is this intake gasket replacement stuff gonna cost me??? It's gonna have to wait a few weeks....short on cash in a major way at the moment.

GRH-
I looked back at my post and I came off like I was flaming you, sorry about that, not intended. You are right, you never know, but he has all the symptoms of the plenum gasket. I hope it's not the plenum, but I would put money on it that it is. He needs to do the tests listed to check the plenum, then look for other stuff.

Waterfoul-
I think I had less than $150.00 in the entire fix. Give your local dealer a call and talk to the parts dept. They are VERY familiar with this fix. The 3.9 V6, 318, and 360 all suffer from this gasket issue.

Brian, is there a website where I can read the test insturctions??

Here you go
 

Thanks Brian.