Just throwing this out there. My 3.9 Dakota had symptoms like your 5.2 and after going thru everything I could think of I took to a garage and they said it was the bushing for the oil pump intermediate drive. I replaced the bushing and drive and that fixed it.
Don't know how many miles you have but it might be something to look at.
If you take the intake off to replace the gasket then do the bushing at that time.