great cold starting, choke idle, steps down to 800 rpm, runs great. gets to operating temperature, operates fine, then idle drops to 600 rpm, gets rough, engine shaking. shut off, cool down, repeats until warmed up. code P0001 = fuel volumne regulator, control circuit/open. IAC replaced, throttle body cleaned, sensor replaced, new plugs and coils installed, all fuses and relays test out ok. no vacuum leaks. ? next steps