cylinder 8 miss fire

Looks like you have covered what they say to do except that there may be an intake leak. Look for any type of vacuum leak, and try snugging up the intake bolts. One other thing is what is the compression in other cylinders? Between all the cylinders they say compression should not vary more that 15% from between the cylinders. If it does then it sounds like a miss.

What was compression on the other cylinders? The 125 to 130 reading may be a little low. Is there any ticking at the valve cover on that side of the engine. Have you checked to see if the push rod is bent or if the valve spring is broken?

I just had my cylinder #8 misfire fixed on my 2010 Dodge Ram 1500 5.7. What the issue was, is that the valve cover gasket was leaking oil onto the boot of the ignition coil causing it to misfire...