I have an N.A fairlane 3.9 dual fuel the problem that I am having
is that it sucks to much air through the throttle body
i have changed the I.S.C and the vacuum sensor on the firewall
if I restrict the air on the hose that goes into the air cleaner
the car runs well if not the car gets to much air and will not run

Is the throttle plate closed at idle? Could have a problem with the throttle cable not allowing it to close properly, or it has jammed in the housing at a point close to idle. In other words may of worn a lip in the throttle body.
Take off the plumbing and look directly at the throttle plate and have some in the car to push the pedal so you can check.

its not getting too much air, its not getting enough fuel.. gas or petrol.. what mixer are you running? does it run ok on petrol but stalls on gas?
could be your gas mixer is foulded up.
Plugs could be burnt.
its trying to suck more air because its trying to get the mixtures right and there is a blockage somewhere, so it can only get ½ of the mix, that being air, and no or not enough fuel.

Then again I could be wrong.. if its been on gas for YEARS.. then its probably the mixer has decided to pack it in.. try it on fuel and see how it goes.. I know it will run like s**t especially if its been on gas for years. if it has been on gas for years it could also be burnt valves.. unless the valves has got hardened seats over time they get killed.. it happened to an old NA I had on gas.. now that was a few years ago..... ahh the memories..

Man the NA was an awesome land yacht.. nothing like a luxo barge to s**t my a** in comfort..

But, I just had to get that XR...

timmeh checked throttle body it was a bit dirty but opened and closed okay d.c I think youre right about the mixture its idling ok but under load
its running rough. but I now have code 29 flashing on the dash
anyone know what this refers to D.C youre right about these fairlanes
apart from all the niggling problems there champagne driving
at beer prices