Well it was a cracked vacuum hose (see pics below). No critters, nests, no "chewing" and no bad fuel. The P2279 and P0106 codes were correct.
On the left side under the acoustic panel there are two small vacuum hoses (3.5" long) that run to the Manifold Air Pressure Sensor (M.A.P.S.). The one that is on the front of the M.A.P.S. adapter was cracked right through at its 90 degree bend. The one that is on the rear of the adapter was cracked too but not right through.
I replaced the hoses with 4" pieces of vacuum hose and the RT ran better than it did in the fall. After idling rough at first start it settled down to a smooth 1400 RPM. No check engine and no LIMP Mode, Yea...my wife is happy again.

A test ride just confirmed this.
I can't see how this will not be a perpetual problem. The forward hose is quite near the forward cylinder. It will dry out from the heat, crack and probably split again. We're going to carry two 4" pieces of vacuum hose in the ever growing spares kit. Now that I know where to look its a 30 minute job to replace them (if the mirror cooperates!!)
Many thanks to everyone for their tips and suggestions.
John
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