Is there supposed to be bolts in there?

Vibration?
Turbo bolts also get loose but not this loose. This probably happened long long ago, but never thought of checking the exhaust manifold.
Is there such thing as too much back pressure?

Exhaust setup: zzp 2.5 catless dp, stock resonator, CTI over the axle piping, Lnf muffler. Boosting 13-15psi on s256.

 

Yes you should have studs and nuts. General rule of thumb for header install is to retorque after a few heat cycles. Looks like it was torqued once and then not checked after heat cycles and they came loose. Also looks like the source of an exhaust leak by the soot like black around it.

 

There are supposed to be studs there. It appears the surrounding area is black from leaking exhaust. I bet this doesn't sound the best. There is a such thing as too much back pressure but that is typically caused from a plugged catalytic converter. Back pressure would cause your engine to choke out though it wouldn't cause your exhaust bolts to come undone. I would guess the studs were over-torqued and broke off eventually. Is there any reason your setup would have excessive vibration? Have you noticed your turbo taking longer than it should to spool?

 

Thank you
Yes I have not retorque them. Or never did. After heat cycles.

One day I found a stud with the nut on it in the driveway, never found where it came from till yesterday lol.
Vibration, just a wild guess. I'm using rotated mounts, don't know if produce vibration like a polyurethane mount (used to have it on my cavalier, and it created so much vibration)
I do notice how loud it is on cold start(that's how started to look for leaks), but once it warms up it quites down and I don't feel any difference. Probably from driving it like that for so long.

 

I would guess that since the studs broke off it wasn't from the nuts coming loose which I would assume happened if your studs were still there but with the nuts missing.

 

Now that I remember,
Vibration, because sometimes the car shakes abruptly (sometimes lightly) when I release the gas pedal while cruising. Not much before but I have been feeling it more lately.

 

Did you drive your car a few days and then recheck the rotated mounts? If the motor wasn't rotated properly when you torque everything down you could have it in a bind.

 

No I did not, rotated mount was one of the first mods. I wasn't very knowledgeable about the car on that time. Joe aka ItalianJoe installed the parts.

 

Even saved it all this time, not knowing where it came from lol.
That's how i found it on the floor.

 

Joe should have known the seq to tighten the mounts.

 

I'm sure he did the mounts correct. It's hard to say if new studs where used for the turbo kit. They could of been damaged by a prior header install and the heat and added pressure from the turbo could of finished them.

 

Thank you for reminding me.
Forgot to mentioned. This is the second header. The first one, zzp's prototype broke in several welded sections, so I had to order the new cast one. So most likely studs were reused multiple times.

 

That could be the reason for the failure. I would replace all the studs to be sure.