Just and off the wall question here ( BTW if i win give it to the Brick id rather see this place stay up and running then take money from a member of it ) have you looked at your turbo here ( well im sure you have ) but if its pushing to much air that will cause you to run lean, keep in mine the turbo forces clean air into the head for the combustion of the fuel to much air causes a lean mixture not enough causes a rich mixture, i had this problem with my 86 740 turbo when i had it, it eneded up being a issue of a few diff items causing this to me and i was running stock too, heres what i ended up doing and finally figureing out what was causing it, first on the AMM there is a screw on the outside with a metal plug over it, its commen for auto mechanics to remove the screw and adjust it to make the air to fuel mixture correct and normally will work if its slightly out of wack so check to make sure he didnt mess with it, then it turned out i had a bad temp sensor so i threw that in, replaced the IAC Motor as it was taking to long to respond to the throttle when slammed down which means it was sticking, and i went through all that you did list there until i came to my fuel injectors i removed them cleaned them checked them all out and reinstalle them and still the same problem though this time my neighbor whos mr car guy ( has rebuilt more engines then anyone i know ) came over and told me a tip to check my injectors while the car was running so he says to put water on the injectors in the little dimples on the bottom of them and see if it gets sucked in if so you have an injector air leak and that shoucld be fixed, he also pointed out a dirty engine will cause all sorts of problems that shouldnt happen, dirty as the inside of the engine, so he informed me of another tip poor some transmission fluid in your oil for around 100 miles 1/2 to 1 quart for 5 quarts of oil, i can say it cleaned everything out and it ran much much better, but still was alittle off so i looked at my turbo and this is where i found the most disturbing problem, after dismantling the turbo for a rebuild since i had it off i found multiple cracks through the turbo mainly where the pressure is, though this is tech not part of the turbo and part of the exhust system, so i would pull your turbo off dis mount the turbo and look at the rear portion ( ill call it part of the turbo ) of the turbo you will have to remove the actuall turbo from the houseing unit to see them, if its cracked it will run lean or rich.