Ryan have you checked your drive shaft alignment lately???
The only reason I ask is because earlier this season I was experiencing a vibration much like yours. Come to find out my alignment was OK, but the bolts/nuts had loosened just a tad.
Need LT-1 parts?
OIL FILTER: Factory installed is a Penzoil P23, Afta market brands, AC Delco PF-454 and a Fram PH-13 or PH-30 will work.
SPARK PLUGS: AC Delco MR43LTS (gapped to .040")
FUEL FILTERS: AC Delco 25171391 (pump inlet side)
89058397 (pump outlet side)
IGNITION WIRES: Call Inboard Online @ (877) 327-7175 and order part numbers 556010A (odd bank) and 556010B (even bank)