Yeah, like I said it really doesn't sound like an exhaust leak, but might as well check it

Did you tighten the silicon clamps with a wrench or a screw driver? I blew a silicon coupler completely off at 9 psi... You just can't torque it enough with the sd once you get a little oil into the charge pipes.

I'd think a cracked weld in the IC would not act this way (it would be open when the IC was cold and closed as you added heat to the IC)

It really sounds like either valve float cause by back pressure on the exhaust valve, or like you have slippery silicon.

 

Hmmmm when I checked most of the silicones, there were some with oily residue on them.. One or two looked very suspicious.. Perhaps I should REALLY crank on them and see if it cures the issue.
I dont know about valve float, I mean we're talking under 6k rpm on '03 6.0L with only 13k miles and 9psi of boost. It even lost boost at 7-8 psi when I turned it down a bit.

 

Is it more rpm related? Just weird. Without seeing it makes it hard.

Clogged cats?
possible wastegate -but doubt it since it works at first.
clogged filter at turbo?

 

may have the answere! I found that the wastegate bolts were not that tight and there appeared to be some black soot around the bottom. This could be a nice pressure loss under higher boost/rpm numbers. Would certainly answere a lot of questions. I'll get out when i get off work and see if that did it.

 

You may have burned the gasket if the bolts were loose -- if it works great, problem solved. If it still acts a bit weird, pull the wastegate and check the gasket (you will immediately see if it's burned).

 

That is actually how I found it, I was removing it to inspect it and thats when I noticed there was a tiny drip of oil right between the wastegate and it's mount and nowhere else, it came from inside the pipe between the wastegate and exhaust. It has the metal seal there, so it just needs to be crushed into place to seal up. I did end up taking it out, but it was too wet and I was losing traction all over the place.

 

NIce and dry out but problem still there.. Get this, even at low boost 5-6psi, the truck will run like raped ape to 6psi then drop down to about 2psi then take off again up to 6psi then drop and so forth... I cannot figure out what the hell is going on here.

 

Do you have another wastegate spring to try?
Where are you at?

 

I'm gonna replace the reference line to the wastegate and see what happens.. I should probable also call STS.

 

Yeah definitely call them. This one's a bit weird

I had a funny issue with not being able to boost higher than a certain point, and it came from having too big of a vacuum line (the installer got frustrated getting the vac line on and used a length of 3/8 fuel line instead) on the boost controller-to-wastegate and it wasn;t sealing on the wastegate nipple past a certain psi (5psi I think). I'm wondering if you are dealing with a similar issue.

Does it do the same thing off the boost controller?