Can you get good brake by pumping the brake pedal?

 

Why was the booster replaced? My guess is you've got a leak somewhere (calipers, wheel cylinders, or master cylinder or perhaps a problem with the new booster). Brake fluid leaks can be hard to spot, because it won't necessarily leak onto the ground. I had a mysterious leak on one of my Toyotas and finally discovered that the back of the rear brake backing plate was a little wet with brake fluid, but it didn't drip onto the ground. The paint on the backing plate was peeling also, and that is something to look for as brake fluid eats away at paint.

 

If the mechanic bent back the MC instead of removing it to replace the booster, they may have damaged the lines going to it and caused a leak. If the brake booster was faulty, you would have a very hard time pressing the pedal.