A few performance questions..

[spenceman72]

Hi everyone. I've got a few questions regarding my 72 K5 and some performance related issues I've been encountering. This has the 350 V8, 4 speed with Granny Gear, headers, Edelbrock 1406 carb.
1. On the carb there are 2 screws on the front to adjust the A/F ratio. When I turn the screw on the left all the way 'closed'..clockwise, the engine does start to really stumble and act like it is going to shut off..then I turn it CC about 2-3 turns and it runs smooth again. However when I turn the screw on the right all the way closed nothing happens. From what I've read, closing either screw should cause a change in the engine, however only the left screw seems to do so?
2. When I first start the engine it will usually fire up quickly, then die unless I pump the peddle...not sure if this is 'normal'? I do push the gas peddle down once before turning the key..I read this is what engages the electric choke?
3. To my comment in #2..the first time I fire the engine up it will usually turnover quickly..but then if I drive for say 20 minutes to the auto parts store and spend 10 minutes there, when I come back to start her up again the engine won't turn over quickly this time..will take 5-10 seconds before it fires up..not sure what could be happening here?

Anyways, probably giving terrible information here for anyone to help with potential diagnoses...I'm not very mechanically inclined, but was hoping I could get some ideas of things to check/look for.
Thanks everyone!