So I’ve got a 99 ram with a 318 and I'm having recurrences of cylinder number four (and now eight) misfires. Anytime I hammer down or go up a long hill or push the truck above 3000 RPM with the transmission kick down, I lose power/speed, my check engine light comes on and now it flashes at me during, and for 30 seconds or so after I let off. High end acceleration is almost non-existent as it seems to take hours to get up to seventy unless I’m going downhill. I've done a full tune-up (plugs, wires) in hopes of curing the issue it worked for awhile….. But now it has come back.
Also I’ve notice lots of oil consumption haven’t noticed any smoke or leaks well a little on start up for like the first 2 sec and not a lot either but I’m not behind it going down the road.
Any Ideas…..

 

https://dodgeforum.com/forum/2nd-gen...um-thread.html

 

Check out the sticky topic "end-all/be-all plenum thread" at the top of the forum, and consider your catalytic converter a goner. Could be that the even bank head is a goner, too. Also, replace that PCV valve with one from the dealer because it's probably what's causing the #4 misfire by oil fouling that spark plug. But the rest of your symptoms are consistent with a blown plenum gasket.