Not Engine Interference Afterall
Culprit turned out to be the aftermarket LED headlights I installed. Key on, engine off, headlights off, fender tip lights off, signature light off- radio works great. Engine on, headlights on, fog lights on, fender tip lights on, signature light on- radio nothing but static. Dealer owner used kill switch to shut down engine, headlights on, fog lights on, fender tip lights on, signature light on- radio nothing but static. After about a minute or so the headlights turned off, fog lights on, fender tip lights on, signature light on- radio works great. Same results after a couple more trials.
Contacted supplier of LED headlights and reported issue. Supplier had not heard of issue prior to my phone call. Supplier going to research availability/compatibility of a plug and play isolator sometime used with HID (ballast) headlights to solve problem.