You will get some good advice here but there may be many variables to consider.
If it were me I would immediately do these quick easy steps to help eliminate and erase some confusing factors so you can move forward with less questions in the back of your mind.-
Seafoam the hell out of the upper intake, pcv intake, and gas tank. Replace with new plugs again. And believe it or not, double check its not a vibration from the clutch cable fork connection underneath that's notorious for sounding like valve tapping believe it or not. But anyway, cleaning up with Seafoam and new plugs helps in the diagnosis.
'97 3.8 Pacific Green
1996 SVT COBRA