Break issues

I have a 1990 Jetta 1.8L. Breaks feel firm but car does not slow down like it should. Pads are fine. Noticed that vacuume boost moves forward when break pedal is pressed. Has anyone else had this issue? Does VW make a retro fit bracket to shore up the booster at the firewall ?

If the booster moves forward when the brake pedal is pressed, it could be the booster bolts are no longer tight on the firewall, or that it takes too much pedal pressure - indicating something else isnt right. Its possible for the air bladder inside the boosters to develope leaks. The result is less 'boost', and a heavier brake pedal effort. Its also possible the inside of the booster is partially filled with leaf bits and mud. I have taken a couple of boosters apart to look inside (though not on my 90 Jetta yet). In each case it looked so mucky inside that I wondered how the brakes had any assist at all.
Please let us know if you find out the cause. (I have two 1990 Jettas I want to keep using for many more years).