"When in 4th or 5th gear if I full throttle at about 2000 rpm-2400 rpm the revs seem to jump, sometimes as high as 3000 rpm."
If I am reading correctly, you are saying they spin up as if you were reving in neutral and then rise as you would normally expect in line with the increasing road speed? But do you detect in that initial phase the car is not responding in speed as you would expect, or that the momentum is linear from that initial press of the loud pedal?