Front engine mount was a culprit for me.
It was really hard to shift especially when the car was cold.. lower gears were impossible
I did however have a vibration around 3k rpm
Changed my mount to 987 one and shifting is much easier now.. it's a simple DIY just make sure you have a flexible head 15mm wrench..
The only hard part was supporing engine with scissors jack while working on mount.. it's scary as hell
Thanks
Sasha