Mileage - more numbers, and upgrades?

[Benjamin Weste Pearre]

For what it's worth, my stock 1990 200TQA's computer tells me I get
about 27 hwy at 75 mph or so, about 19 in the suburbs between San Jose
and San Francisco, and rarely more than 14 around Boston.  Doesn't
change a whole lot with temperature, seems to drop an mpg or two in
heavy rain (more rolling resistance over wet pavement?)

I'm thinking of chipping the old car, and I was wondering what
experience people have had with mileage post-upgrade.  I'd think that
it would help somewhat given the same driving style, but I've heard
conflicting reports.

Also, someone mentioned something about ECU upgrades and high
altitudes - apparently the turbo can spin too fast?  I live in Boulder
and not infrequently drive up to about 12000' (briefly).  Is that
considered "high altitude"?  I don't really understand what the
problem is, whether there are things I can do about it, whether it's
something I have to worry about with an ECU upgrade, whether I have to
worry about it already...

Cheers!

--
Ben Pearre          1990 200TQA          http://hebb.mit.edu/~ben