Mystery limp mode

[R08]

I have a C250 manual
Around town the car will rev above 3000rpm and drives completely normally. When I'm on the motorway, it won't go above 3000rpm but also performs normally up to that point.
There are no warning lights or codes. It's been put on a star diagnostic and nothing shows up at all.
Any ideas what could be causing this issue ?
I'd rather not take it to a main dealer, they could strip my bank account looking for a solution !

 

[Trickythemerc]

You need to have the live data read whilst the car is on the road, can't understand why it is not showing any stored codes though.

 

[R08]

You need to have the live data read whilst the car is on the road, can't understand why it is not showing any stored codes so

You need to have the live data read whilst the car is on the road, can't understand why it is not showing any stored codes though

I can probably take it to a garage with a rolling road not too far from me, they would be able to see what's happening I'm guessing ?

 

[Yettie]

You haven’t got a speed limiter switched on ?
Does it rev past 3000 on acceleration ?

 

[R08]

You haven’t got a speed limiter switched on ?
Does it rev past 3000 on acceleration ?

No speed limiter on, it will very gradually get up to 100+ but it is very slowly to do so, it just will not rev above 3000rpm unless I'm for example, in urban situations and lower gears.