One cylinder not firing

[SableSlayer]

I went thru a lot of this and it ended up being my lower intake gasket. On mine the gasket was blown out around cylinder 2 and 4 causing an internal vacuum leak which was taking my long term fuel trims up at idle.
If it was your distributor being off you would get code 1345
Did this start before or after changing injectors?
Here's a photo of what was collapsed on the intake gasket

 

[rdobirdman]

It started before I changed the injectors. I've been wondering if it might be intake gasket problem. Were you able to diagnose the leak before you took the manifold off?

 

[rdobirdman]

Anybody got a way to test for internal vacuum leak/intake gasket leak without having to take it apart and look at the gaskets?

 

[L31MaxExpress]

If it has not been apart in 3-4 years for gaskets, I would pull it apart and do them anyway. I only run fiber paper gaskets on these now.

 

[rdobirdman]

UPDATE, problem fixed!
I finally got time to pull the intake manifold to replace the gaskets. Didn't find a smoking gun, the gaskets looked fine, no obvious problems. Anyway I replaced them with the Felpro gaskets and got it all back together.
Fired her up and it's running great on all 8 cylinders now.