Idling high ? Need some insight

[alwaysbehind09]

I have a 99 tahoe that is idling extremely high. About 1200 rpm in park and 900 in drive. I have replace spark plugs, wires, dist cap, rotary button, iac, and cts. No change. I am still getting a code for faulty iac and #6 misfire. Can someone lead me to a solution. Bout to just junk this thing if I can't fix the high idle it's driving me insane. Thanks!

 

[lesterl]

Check for vacume leaks, also how does the plug on the #6 look, wet/black/clean?