easy to do with a can of WD40 and a paint brush.
its just a rotating half cam in an air chamber which is controlled by a motor.
lets/dont air through.
simply gets gunked up with oil deposits and wont turn around
what i do is to fill it with wd40
put thumb over holes and shake like mad for about 5 mins then stick it on an old cb power supply (or something with low current output NOT A BATTERY!!!) after giving the surfaces a good scrap / brush to get the hardened black deposits off.
its quite a hardy bit so dont be afraid to scrap hard.
if it dont move still.
twist a driver infront/behind and work it back and forth from both access holes when it is clean it should rotate very freely with just a light push it will be a pig to do the first time but very well worth it.
it makes the motor pull like new once done.
there is a guide on the net
http://82.34.50.33/sytemsandsoftwar...automotive/How_to/General/ecotecidlevalve.htm
one tip:
watch the rubber membrane, make sure it either sticks and stays to its housing or comes off with the valve. else it will split if it sticks to both surfaces, use a blade to easy it off ..
however. i doubt this is your only problem by the sounds of your description but it is a start.
let me know
mike