My 1988 6000 2.5L (125,000 miles) kind of does that too if it sits for a
long time - you hardly touch the brakes and wham.  Fortunately, when I take
it out on the road, the brakes work fine - it just does that in the
driveway, and it only does it when it's sitting for a long time.  The brakes
have never really been good on these cars in my opinion - even with my new
brakes on both front and back, you still don't slow down if you lightly
touch the brakes.  When I drive my Grandpa's 2005 Malibu for example, when I
press the brakes as hard as I do on my car because I'm used to it being that
way, it brakes really hard in the Malibu almost feeling like I stomped on
the brake.  (Well, maybe not quite.)  But back on to the topic.  The brake
pedal does not go to the floor, so it would appear that my master cylinder
is okay.  Then a year or two before that, my brakes would lock up, but even
so, it didn't feel like it was stopping me hard because it was just the rear
brakes that were locking up - it turned out that both wheel cylinders were
leaking, and in addition, my entire rear brake sytem pretty much needed
replaced.  The mechanic said I was lucky I never lost my brakes completely,
and I had gone on with that car for three or four months that way.  You'd
also feel a thump everytime you'd let off the brake from a stop.  It only
ended up costing me a little over $300 for the whole job, and I also had a
transmission fluid change as my tranny would not kick in a time or two when
I went to press the gas for a second or two - the change fixed that
fortunately.  Now as for the gas about it being touchy, if you don't let my
car roll before you press the gas when you're from a stop, it on occasion
will stall (it's always done that in the nine years it's been in our
family), however, if you don't let it roll and you press the gas and it
doesn't stall, I can agree with you that it gooses just a bit when you press
the gas.