Decided to attack the issue with no compression on #4 as my top priority, I removed the passenger side head cover.
I can't see anything obviously wrong with it. Here are the closer looks at cylinder #4

 

Looks like I will have to remove the intake manifold in order to remove the head. Moving to the driver side and I was able to disconnected everything relatively easy until I reached the EGR connection. I don't have anything of that size to loosen the nut. It's time to put things away and go shopping.

 

My trick for loosen EGR nut: 12" crescent wrench with DIY extension bar

My head keeps hitting the hood and it seems like the hood can't be raised vertical. Such feature would be nice for this job.

 

The upper intake manifold piece is out. Not sure if this looks normal for a 170k miles rig or not. Carbon build up and heavily deposited carbon on EGR chamber
A closer look

 

Here is intake manifold lower piece. Next two items to order are intake manifold gaskets GM 12559099 and GM 12559098.

 

To remove the lower intake manifold, I will have to remove the fuel rail and the distributor.
Released the fuel pressure

 

The #4 connection on the distributor looks suspicious See how it wasn't pushed all the way in? Should connections be pushed in all the way to ensure contacts? Is it too late to stop or should I go all the way?

 

Removed the distributor and found corrosion on #4 connector
#4 plug to connector
I think I am going to stop here waiting on the expert to tell me if it's worthiest to go all the way or not. Happy father day to all!

 

That could be your issue for sure. Not suggesting what you should do..I'm lazy. I might roll the dice and assume that this was the issue. It sure looks like a genuine issue.

 

Those corrosions are from the sparks right? The distributor and the wires were replaced last March 2017. And that mechanic is willing to pay $2000 for this rig where the book says it worths under $1000. Something is fishy about this whole thing.