A hard pedal means the booster is not doing its job.

Check the one way valve on the booster (the plastic piece in between the line and the booster) You should be able to blow in it one way but not the other.

Testing your booster with a vacuum gauge

http://www.type2.com/library/brakes/vacboo.htm

88 4R, 350 V8, R150 5 speed Sold <...uot; />
97 4R, stock, daily driver
98 Sienna, kid and dog hauler, wife's ride