This first started at an autocross two weeks ago....finished my run & pressed the brakes hard (they worked perfectly) as I went through the finish & shifted into neutral to check out my time....suddenly, with the brakes pressed, the idle jumped up to 2000 rpms & oscillated up & down for the next couple of seconds.....This happened after every run - the brakes work perfect but the idle jumps....

Now, if my prelude is just idling in my driveway & I pump the brakes, the idle jumps up to 1500 rpms & then to 2000 rpms before coming back down....I checked for leaks between the brake booster & the intake manifold & can't find any....Could this be a possible sign of brake booster/master cylinder failure or is there something I'm missing?