This is going to sound totally unacceptable but the cheapest route you can go to achieve higher vacuum is to change the cam. Yeah that's right, change the cam. That must be some lift and valve overlap you have if the vacuum's in around the 13Hg range. Pedal ratio is not going to help unless your manual, period, your car is currently vacuum boost and won't brake without the proper amount of vacuum. A bolt on hydro boost from the auto recyclers - $125 + another $200 for plumbing, a decent electric vacuum pump ( with enough suction ) $300 + wiring and possibly a newer alternator to run it another $200. Don't forget your hearing protection cost - those things are noisy and as annoying as outboard electric fuel pumps. You could triple up on the vacuum cans with a check valve but the bottom line is "low vacuum is low vacuum" and a million cans aren't going to increase it. You need 18Hg minimum for proper vacuum brake systems. So in reality there is no, I repeat no way to improve braking in a cheap manner. If you do opt for a vacuum pump, bite the bullet and buy a vane stye that runs off your existing pulley system. Their the most reliable, produce huge amounts of vacuum and look snazzy. Or you could just change the cam, after all it is only a daily driver.
