Any ideas what this could be??

[Steelepuls]

Were you decelerating or accelerating? 80mph on a S with a 6spd trans gets you about 3000rpm, which is usually when the engine vibration from the motor or transmission mounts start vibrating when it is decelerating. I bet if you go about 85 and let off the gas to decelerate, the vibration will come back right around 80mph and stop somewhere below 77mph. It does that with mine.

Flmont is right it could be engine and trans mounts. Or the coil packs might be going bad, it didn’t say you replaced them, do you know how many miles are on the existing ones?

I’m still trying to figure that vibration or shudder at 3000 rpm (on any gear) in my car.
I’ve replaced the motor and trans mounts, spark plugs, tubes and coil packs. Some people here say the motor has natural harmonics at that engine speed. LMK if you figure it out as well.