Erratic reving (very odd)

Hi Folk's......
My Freelander has developed a very unusual fault wich has got me well and truelly baffled!
It runs fine when cold but after 5-10 mins of driving won't rev normally, all I can explain it's behaviour is the revs fluctuate erratically when the accelarator is pressed.
Checked for spark- Kv is spot on
Checked for fuel pressure-ok at around 3bar
Checked throttle body- Clean and moves freely with throttle cable
No fault codes
Any help appreciated

First thing I'd do is clean the iacv.

cleaned out the iacv, It idles beatifully but still won't rev above 2000rpm when slightly warm.
It is almost like its hitting the rev limiter at 2000rpm then it chokes up (deep groan from the inlet) proper head scratcher :wtf:

Did the fault start suddenly or gradually get worse? Is it a dizzy model or a dis system?

Could be an air leak on the inlet manifold mate

Its an 03 wasted spark system....
did a smoke pro test to check fo any crankcase breather or vaccum leaks and all ok
the fault has occured suddenly it's almost like its loosing fuel pressure as it warms up, I'm wondering if it might be an ecu fault with all the wet weather we've had, obvoisly some more thoough checks will have to be caried out.
I have litterally checked for any sot of mechanical faults it could possibly be and all seem's to be ok. Would have to happen just before Crimbo!