So, put on a new set of continental extreme contacts.
Not the bestest but for me, the smooth, quiet ride is worth it.
Solved the vibration (mostly) in the steering wheel, staving off the lower arm replacements for the moment.

What this enabled was focussing on other things.
Most of my traffic is work commute. About 4.5 miles each way, mostly stop and go, lots of lights.
Noticing when press the Go Button slowly, there is a delay in the trans engaging. Or maybe it just goes quickly to second gear?
If I’m first at the light and I give it more juice, all is good. Smooth and second kicks in around 25-30mph.
Is this normal? Is it part of the throttle training I read about on here recently?
Curious.

 

I'll make two comments ($0.02 worth). I put new Continental Extreme Contact Sport 02's on the Ferrari this summer. Very pleased - good combination of ride quality and performance. I think I would put them on the XK next time it needs tires.
I have not experienced any trans engagement lag with gentle throttle as you describe. What tires were on before? How old and how worn? Brand new tires with full tread will definitely give a different feel until you get used to them. Full tread is going to "give" a little more than tires that are down to 3/32nds. Not sure about the "throttle training" thing.

 

Bought it a month ago with Michelin Sports.
Had decent tread, but the manufacture date was 10y ago, so I knew they had to be replaced.
Given The vibrations on the old tires that went away with new, I’d guess they were unevenly worn and dry.

 

Slight lag, yes.
I don't recall, have you changed the transmission fluid and filter? The diff fluid?
That may also cause a feeling of a minor lag.

 

Not since I bought it. Previous owner said he did the full trans service a few years ago.
but it isn’t an expensive item, so may do it again.

He also said he did the Diff. But in both inspections, there was signs of a very very small leak in the I think diff seal or vent or something.

 

Lag... maybe an air leak. Maybe due to something flexing. Watch OBD as lag occurs.

 

I have my OBD gauges on every time I drive.
LTFT is zero at idle and around .7 cruising. If I stomp the go button it peaks to 1.78 then settles. Highest I’ve ever seen it was a quick blip around 2.5

Flexing part tracks, both motor and the trans mounts need to be replaced. Doing that in a couple weeks.
So there is slight vibration and occasional wiggle.

Is there another metric to watch?

 

If it's a momentary leak you'd see it in STFT(s) but not lin LTFT(s).