I have a 97 LX450 with 295K miles. Yesterday morning I was backing out from the driveway and when I pushed brake pedal it became quite hard to push, but I was able to stop. Today the same thing happened when I was about to park the truck. I checked and had to ad a bit of brake fluid, but it didn't help. Does it sound like a vacuum problem or a brake booster is going bad?? Any Ideas........... Thanks