My brakes burp!?!

[Mgoeller <mgoeller@brightok.net>]

I recently acquired an '87 5ksq w/97k miles.  The car is in immaculate shape
in and out.  The only problem is that the anti-lock brakes burp when the car
is rolling to a stop. Also, a small wire on a warning switch on the
hydraulic brake booster (directly behind the master cylinder) was unhooked
and when hooked back up causes the warning light to come on.  Is this caused
by the hydraulic modulator or the pressure accumulator (aka the bomb)?  

I have checked the brake booster by removing the return line, but no fluid
leaks by.  The brake pedal is stiff and does not have much movement, while
the car is on or off.

Has anyone had this problem before and what do I need to check?  I do not
have a very good repair manual to assist me in my quest.

Thanks in advance,

Mark Goeller