Here is a good one, 77 chevy k-10 pickup 4wd. 350 4bolt, mild rv cam was smooth idle. I have a performer intake with a 650 vac, sec. carb. Ok, built this motor in december got it running had problems from the get go when it warmed up idle drop, so decided to try a different carb, that was a big performance change but always would kill you standing behind it, tried increased timing, went from 44 plugs to 45 it carbons them all up, so I have dealt with that for a while now, I have had a vibration in my shifters at 2200rpm, so I just shrugged it off as the new clutch being a tad out of ballance, I was driving it for about an hour a couple weeks ago and I got into it ran it up a little ways then after about 25 min the motor idled down started running like it had about a 292 cam in it choppy choppy, so I tried to adjust the floats nothing, so heres a kicker and cant figure this out yet run the mixture screws in normally in all my years the motor will idle down, not this one, bottom out the idle screws it idles up, ok weird to me from having about 10 holleys over the years, so I replaced, coil, ign module, plugs again, cap rotor you know thinking I may have weak ign, nope still runs the same, so I decided to hook vac gauge to it, yea I know took a while huh, fluctuating from 10 to 17 very fast, so here I am carb has never acted right with the idle mix screws being like that, and now it runs like it has an internal problem, It will still run, I just never have figured out that running rich all the time at idle, did everything now and I am at a road block, tried floats, needles, power valve, so anything to suggest I am pulling valve covers tonight to inspect and probably going to pull the carb off again to see if I can find anything!