D24 misfiring on cyl 4# at idle

[Echo1975]

So I have noticed that for a long time the engine has had a bad shake at idle so now I finally decided to find out what's wrong so I started cracking the injector lines and opening cyl 4# line makes no difference to the way the engine runs even though fuel started spraying from the line.

The engine smooths out at about 1200 rpm and runs like an inline 6 should but at idle it shakes like a 3 cylinder.

Also the exhaust manifold is 90f cooler coming from that cylinder than the other cylinders.

I did a compression test through the glow plug hole and it went to over 320 psi instantly and that's where my gauge maxes out.

I think that leaves the injector or the injection pump as the culprit. I checked the injector spray patterns around 6 months ago and all were good but I couldn't check the opening pressures due to the gauge not functioning on my test tool.

If the opening pressure is wrong, will it cause a misfire resulting in cooler exhaust temps?