I bought my K5 with the Edelbrock 1406 already installed, and after cheching it out initially, I didn't realize that the idle was too high, 1100-1200 rpm. When I killed the old engine and got the new crate 350 in and put together with the used 1406 and brand new performer intake. So I got it all fired up and went to tune the carb, and could not get the idle down below 1200rpm. The idle screw is backed all the way out (not even touching the throttle lever). I have taken all the vacuum lines off and plugged them and checked everywhere for vacuum leaks, but to no avail. I read a post on here once that said that something with the throttle plates and/or where they seat on the carb 'body' may be worn, thus allowing some airflow and causing the high idle. This might make sense to me because when I first got the K5 the idle was WAY high, like 1600rpm. The truck would try to take off as soon as I let my foot off the gas at stoplights and stopsigns. I remedied this by adding TWO more throttle return springs to hold the butterfly's closed. Because of all the springs, it makes for a very stiff skinny pedal. So, armed with this info, what should I do about the high idle? What if the butterfly's are, in fact, not seating completely when the throttle is closed?