Advise on a S4RS mod. 2006

Hi,

I live in Norway and had a VFR, VTR SP2 and now thinking seriously to buy this used bike:

I went trying it and here are my impessions:
It breaks well, accelerates well, but I felt the rear suspension was maybe too soft, or when I was giving some gas, I felt the front was going too much upwards (not that much acceleration to do lift the front).
for some reason, I didn’t felt confident in taking turns with a bit of speed (front felt a bit upward in relation to the back).

The seller has lots of parts original.

when I was giving some acceleration, I heard a sort of a sound like pshhhht coming from the reservoir (air filter). Is that normal?
Also, air filter is washable.

No cracks on the instrumentation.
lot of vibration on my right foot which makes me think there are loose elements.

the bike started up fine when it was cold but struggled when it was warm.
he said the previous owner changed the regulator.
the blinkers were blinking just fine but the front light was a bit weak

Any advise please?