Reduced Engine Performance - Throttle Body? ETM?

I picked up my first used Volvo on Saturday (2004.5 S40 T5) and within 30 minutes of owning it the on board computer was giving me the message "Reduced Engine Performance". After a good search on the forum and bit off googling it sounded most likley to be the 'Electronic Throttle Management' which seems to be a common problem, yet expensive. Took it back to the dealer (independant) as I got a 3 month warrenty with it, and they've taken it back off me to sort out (as you would expect). I hung around long enough to see what the diognostic tool said the logged fault was, which indeed was the throttle module. They have said they are just wating on the part 'Throttle Body' and they'll fit it, all sorted. BUT, my question for anyone who has come across this before is: is the 'Throttle Body' the same thing as the ETM (Elecrtonic Throttle Module)? I just want to make sure that the fix being proposed isn't a half way house and that its the right part getting fixed!! Apart from that the cars in great condition, so I hope this is the only problem. Well, not the best start to Volvo ownership, but its not put me off just yet so long as it is what they say it is!

My understanding of the throttle system was the that the Electronic Throttle Module was the electronics which figured out the position of the accelerator pedal and controlled the Throttle Body's butterfly flap to regulate power to the engine. I had the throttle body cleaned out on my S40 2 weeks ago as the car was suffering from uneven idling, fixed it a treat. From what I could tell the throttle body was just an air-intake regulated by a servo-controlled flap. Think the ETM is a separate box of electronics somewhere.

Yeah that would make sense, cheers for the reply. After you've mentioned that, I think it is likley to be something like your problem, rather than the ETM. Mainly becuase the problem doesn't occur when using the throttle, but at idle, I'll keep my finger crossed that thats all it is! :-)

Quick update: 

The garage has now replaced the throttle box under the warranty and say it hasn't reproduced the 'reduced engine performance' error since. I guess time will tell, hopefully they're right! and this will be my last post on this thread! :)