1988 454 TBI problems

[LeRoy]

Here's the skinny. Arratic idle, idles sometimes around 1500. Cold starts, it immediately revs to about 2k and takes its own sweet time coming down to low idle which is around 1k. I think low idle should be around 800 RPM. New parts include O2 sensor, new TBI base gaskets, and now a new IAC valve. Thought for sure it was the IAC but with the new one in. It runs worse with the same above problems. So what do you experts have to say? Thanks in advance