Revving problem

[Isabo]

I posted this on the Boxster forum with no joy. Any engine gurus care to chip in? I've just bought a 2.5 Boxster as a surprise present for my daughter. It's only intended to be a fun car for sunny days as she has a daily driver Honda and is more into motorcycles anyway. It's going into the bodyshop tomorrow for some minor dings, stonechips and touch ups.
The problem:
It revs fine up to about 5500, then it goes dead like it's hit its limit then opens up again around 5800 and to the redline. The car was owned by a woman who mostly used it for pottering around town, it's overdue for a full service and has 50K miles on it, smokes a little on start-up (less than my 911). I'm hoping to get away with plugs and leads for a fix (ever the optimist)
Any thoughts on possible causes?"
In case anyone is wondering no I didn't get a PPI, I saw the problem when I tried the car and my offer took it into account. (It was a killer deal!)