Hello folks,happy new year and heres hoping someone out there can help me.

My 535i is playing up,it started about a month ago and has got seriously terminal now.
The car starts ok (runs a bit rough though) and in park or neutral seems ok
but when you start to drive between 1500 and 2000 rpm will not pull at all and then the revs drop the car gives no reaction to the gas pedal and then cuts out (not that great on an automatic no brakes , power steering etc etc).
Have done the usual filters (gas and air ) plugs ok but changed them anyway
and set them at 0.86.
Have been told that it is probably a fault with the air intake valve?

Can anyone help out there please as i want to keep the beast on the road because having a British licence plate in Italy saves me money on all aspects of motoring plus the car even though its 17 nearly 18 years old for me still has a great deal of life in it .