Spyder550

Hi can anyone help?

Just bought a 99 T 2.0 Impreza Sport a week ago, with 53000 miles on it
Generally happy with it, but am trying to ascertain I have a problem with it or not.

It feels a bit like driveline shunt occaisionally when I lift off to slow down a fair bit, say from 70mph -> 40mph.
May be just a sympton of have a 4WD system and a centre diff, (brought up so far on 2WD's) so am unsure.
Secondly it appears a bit hunty around 2500 revs at say 35-45mph

Any ideas

Thanks in advance
Guy