newbie with idle problem

O.K. until 2 weeks ago the only thing i knew about engines was that they were under the hood. 2 weeks ago i bought a 85 chevy silverado. 162k miles 305 smallblock. The previous owner butchered the carb(quadrajet) and all the vaccum lines.Somehow it still would limp along.I bought the Haynes manuel and started trying to repair the damage. Had the carb rebuilt(by a mechanic).Replaced allspark plugs and wires replaced rotor and cap bought new pcv vale and breather and new vaccum lines. Put it all together. Got it to run ok but got only 4mi to the gallon and flooded at high rpms. Had a different mechanic look at carb , but he couldnt fix leaks it was in bad shape said i should replace it. So I bought a factory remanufactured carb and solved MOST of my problems. But now I cant get the idle right. It idles ok in nuetral but when i put it in gear rpms drop to low, gets real shaky and will sometimes stall. Timing is set to 8degrees btdc havtried 4,6,10, and twelve . Both mixture screws out 4 turns. Not really sure how to adjust from there.. Idle speed screw in about 3 full turns.

There is an air intake screw on the top of rochester carbs. try bringing it out/in one turn. Dont go overboard, but it should do the trick.

this may soud dumb but is a Quadrajet same as a rochester carb? If so which screw they all look like screws that hold it together..

will take a picture tomorrow after work..

Problem solved..!! Last week I used the advice i got on this site to replace carb(leaking gas at seals). I have found that gas will weaken vaccum lines and make them soft..Replaced the hose going from carb to pcv valve. Slipped right off, no seal..If there is one thing i am learning about engines is the smallest and cheapest parts or pieces can go bad or wear out and seem like a big problem driving down the road..Thanks for the advice and this site!!!!!!!!!