I still think it's your motor mounts. Uphill would cause the engine to vibrate differently against the frame. I would try to completely unbolt then re-seat your engine. Also, change from factory threaded rods to M6 x 50 and M6x25 threaded bolts (get some lock washers). Good luck!

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“The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” - Mark Twain