My 85 22re did this a few years ago.<BR>This may bear no relation to your V6 problem, but I'll throw it out here anyways.<P> In my case there was a plastic one-way valve in the vacuum line running along the top of the fire wall over to the brake booster. This valve had taken a dump and was causing the cyclic rise and fall when the brakes were on while sitting at a stop. A new valve was a few bucks at the dealer and was simply a matter of removing the old one and slipping the new one onto the vacuum line.