Idle question

[Hugh Mongus]

Hello, I am new here, at least to posting. I lurk around and read all the great information everyone shares.

I recently bought a '71 short bed with a 355. When I got it, I made it about a mile down the road, and we got to sit together for four hours getting to know each other while waiting on a tow.

Since then, I replaced the carb, plugs, wires and set the timing. It starts and idles like a champ now. The only issue I have now is when I drive it the idle is too high when I stop. I have added two stiffer throttle springs, but this doesn't seem to help. Keep in mind it idles perfect in park.

Can anyone tell me what my cause this?

Thanks in advance.