"any ideas on how to get this old coffee out of the seat foam without taking
> the seat apart...?"

Chris, if you'll keep doing what you are doing, eventually the amount of
residue in the foam will begin to dissipate. I had a stainless thermos, full
of coffee, "explode" while it was sitting on the psgr. seat, while the van
was in PHX in June/July at Karl's while the tranny was being fixed. He did a
hell of a job of cleaning and that's what he faced but at least it was
caught early .... more recent probably made that a little easier but still a
patience-job. I finished the project after getting the van back home. One
thing that will facilitate extracting/pulling the stain out of the foam:
once you've been working on it awhile and it's pretty damp, put a fairly
water-loaded sponge on it and let the water drench into the fabric and foam.
Go to a car wash where they have strong vacuum's and while using that to
pull the water + stain back out, have terry towels to catch/wipe the stain
and water off the fabric surface. Maybe you have a shop vac that will work
for this?

Eventually this will get most of the stain out, just takes time and
patience.

Good scrubbing ;)

bob