I have a 1990 Mustang LX with a D.S.S. 357, it has a single plane intake and a Hi Lope cam combo, and it has the required vacuum booster kit with a elec. compressor installed. I bought the car with everything done already, now the brakes are getting harder and harder to press, I have been told two different things, the first being that the canister is bad, which is a quick fix and the second is that the vacuum pump is going bad, but the pump and the compressor sound the same as the day that I bought the car and the only difference is the the amount of pressure that I have to put on the pedal for the brakes to ingage. If somebody has had this problem before or knows the solution please let me know. Thanks

 

Usually on a stock vehicle, a sign of a bad brake booster is a very stiff pedal. Basically the booster is leaking internally. You could take alook at the booster check valve to see if that is working as it should or test the booster itself

 

+1 on dreamer1uk's post. Since the problem started after you got the car, odds are it is the booster itself.

 

Any updates on your issues?

If you need a vacuum pump to test your booster, most autoparts will sell them. Just remember you need at least 14 inches of vacuum for proper booster operation