hi i have a diesel freelander t reg the problems i have are irratic tickover [surges up & down] smokes on acceleration , doesn,t feel like the turbo is working so is there a test i can do to check the turbo & i have heard that a common trick is to disconect the propshaft to disengage perminant 4 wheel drive & gain extra mpg as this is only driven on roads so any help advice appreciated thanks