2006 Cadillac STS V6 3.6L 130,000 miles.
Issue: idles at 800RPM, at those RPM, surges, rough, rattling noise. In park, push on gas to increase to 1000rpm, goes away. Driving no issue over 1000rpm, traffic, feather the peddle it stalls, reverse stalls, tight turns in parking lot or drive thru it stalls.
What I've done: plugs changed, air filter
changed, coil pack inspected no cracks, no visible vacuum leaks, oil filled, throttle body and plate cleaned, injector cleaner lots, Lucas put in, fuel filter
inspected is clean, battery and alternator
at 13 to 14v, re secured battery posts, no change.
Is this a common Cadillac issue? Where do I go from here?