98 ram 5.2 help needed

Interesting, I had the very same trouble that took forever to find the issue....
This was what I found in my situation, it may not be yours but worth a check and easy.
Pull the distributor and check the bushing for the distributor shaft pressed in the bock. What I found was the bushing worn so badly it caused the gear to wear out (the gear that rides on the cam and goes through the bushing and drives the oil pump. This wear was not noticeable just looking down in the block (except for gear teeth worn). Put a large screw driver in the slot on the gear top (where the distributor goes) and move it all over, check for slop. I found that misfiring and bucking at idle and under load was because this bushing was crap and caused the movment of the distributor and misfires....once I replaced the bushing, all was great once again! I also found oil in the intake (very common on these) as other have mentioned. I fixed that as well....but it was not what caused the issue I had nor did it fix it.
This took for ever to find an I have never had this bushing go away on any motors I have had. Well it's worth a check, easy and cheap as well!