my wife has had problems starting her 89 240  the past couple of days.
she turnes it over and it fires but doesen't catch until about the
third try when it is cold. then it runs perfectly, idles nice.

I completely rebuilt the engine at the beginning of this year ,
rebored it, valve job , the works.
a new cat and o2 sensor, right after the rebuild got it  through
emmissions. ( and dropped the emmisions by a huge ammount)
after the o2 sensor it ran really smooth.

it still runs great  and doesen't overheat, the power is normal , no
pre ignition noises, smooth steady idle.

I took out the plugs and they had a whitish coating, not tan.
I replaced them with platinum plugs hoping that might help, but must
be too lean.

I was thinking maybe it could be an air mass meter problem?  
anyone know of the symptoms when that fails?
the  ignition wires are new, and rotor are fine.

anything I can check?  I do have a 1990 245 as well so  I can use to
swap parts  for troubleshooting. I was thinking of swapping the air
mass meters to see if the problem moves. does it need to be calibrated
or can I just switch them?

or maybe there is some sort of cold starting mechanism to richen the
mixture when it is starting, that isn't working ?
I am baffled , any suggestions are appreciated.

Phil