My 2005 type X 3.0 ocassionally turns off/on from once to several times when accelerating away from a stop. Check engine light comes on and set code for lean bank 1 and 2 plus two other codes that my scantool defines as undocumented, $87 and $9c. Any ideas?

 

A guessing game... - my first guess would be an intermittent ground contact. Check the ground contact that screws onto the transmission under the battery...

 

And a second guess:

An acquaintance, who is praising a certain local garage, which however is currently unable to fix a car, which at random drives and then stops to drive on, asked my for help.
The garage already pinpointed the cause:
The fuel pump relay.
The problem car here is a Honda Legend from '91, and the fuel pump relay unit there is a separate little black box.
First he quizzed me on the phone about it, and I told him 2 things:
1. A Honda is not a Jaguar, hence, my knowledge there is very limited.
2. Check for cold welds on the PCB with the relays...

Well, I am not sure about his "fabulous garage/workshop", as they apparently - even with my info above - could not fix it (and they could not source a replacement part either).
Hence, he just gave me the little black box yesterday to look at. Today I had a minute to look at it:

It was exactly as I said: The were 2 relays on that little PCB in that box: All 4 solder-points of one of the 2 relays had cold welds (the gaps were that big - a blind man could see it), and at least 1 of the 4 solder points of the other relay had a cold weld. I re-soldered all 8 points and just return the part to him.

Thus, a cold solder point in the right spot may also the reason for your grievances.