R129 SL 320 V6 Kickdown problem

I have a 2000 W reg Sl320 with the later V6 engine
When I press the throttle pedal to the floor to kickdown the engine just revs up and not much happens.
If i drive normally the car goes through the gears fine with no issue.
Any ideas as to what could be causing this?
Sorry if this has been covered before

 

There are many possibilities, but I would offer the airmass meter as being the most likely cause.

 

You could always unplug the MAF and try the car, it will not leave any code

 

I learned on this forum that members having your symptoms cured it by new MAF. However it Could be something else but try maf test first as above

 

I assume you have done the most basic check - ie the ATF level is not low?