Lean Burn Not Working. Massive Headache

[ceeyx]

hi all

i have recently bought a 98 avensis estate 1.8 7afe

the problem is that the lean burn mode presumably doesn't work (mpg is way to poor)

so i was wandering, is it possible somehow to switch off the lean burn mode or enforce the engine allways run on enriched mixture without diagnostic tools. previous owner seems to have done something to the car that doesn't seem reasonable to me (the butterfly valves on intake manifold were disconnected and were allways closed , has any1 any clue why 1 might choke the engine?)

any clues would be apreciated