[SuperHart]

I had exactly the same problem with the dual quad setup on my 351W. Although my engine is different I still use the 427FE medium riser carb linkage and run my carbs reversed. I found that the throttle plates on the REAR (secondary) carb were not completely closing unless I "blipped" the throttle. I had a return spring only on the linkage itself. Nothing I did corrected that problem UNTIL I added a return spring to the secondary carb throttle arm. Yes, doing that made the accelerator a little firmer but more than made up for it by eliminating the fast idle problem caused by the throttle shaft sticking at slightly open position. Try it, I think you will find that it works especially since you claim that your carbs seem to run just fine otherwise. One last thing, if the nuts retaining the carb to the intake are not snugged down evenly or if one of the nuts is too tight that might contribute to such a problem.