250 high idle troubleshoot. Please help!!!

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I have an 81 k10 250 i6 that I believe has the integrated head. The idle on it is VERY high and it sucks gas like no other. Sometimes when I start it the idle is a little lower and it sounds much better, but once I hit the gas and let off the idle goes back up. I'm thinking maybe the Choke is stuck? Just put a new carburetor on it a year to a year and a half ago and I don't get what the problem is. The Idle is only really high in Park or Neutral, when I put it in to drive or reverse the idle goes way down, but sometimes after I hit the gas once I let off it goes up slightly again. There is also a decent amount of slack in the throttle cable.. Maybe too much? Please help!!!!