1994 blazer bad Idle

I have a 1994 Blazer with a 350 engine 155,000 miles. The problem that I a
having is it is idling bad, like if there is a bad spark plug or wire. I
Rebuild the Heads and replace with new gaskets. Found out that the intake
was cloged at the egr valve,Cleaned out and check egr valve. Replace the
Fuel injectors. Replace all the senosor that the Check Engine light had.
The check Engine is off. Replace cam,(stock) It is running stronger but
still Idles bad. I took it to three mechanics and they could not fix that
problem. Does any one have any ideas. (Please Help)

Thanks