Touchy brakes so bad skid left rear wheel, new booster, no brake lights when applied normally. aftermarket cruse control. getting 18 vac in vaccume.

Could be a bad brake switch. Check and see if you have brake lights. You can pull codes from the BCM. Takes a scanner though.

I had my power brake booster go bad and I replaced mine as well as bleed the brakes that when I went and tried them out 'I slammed on my breaks early before getting to close to the light' that my car left skid marks all over that road because the brakes worked like power brakes should and yours sound like your booster was installed wrong or the pads are bad or you didn't bleed all the air out of the line. Your problem you described was like it felt before I replace brake booster ie lousy non power brakes when I had power brakes.

Check your rear Emergency brake shoes inside the rear rotors. When the brake lining falls off of the metal backing, the linings get ground up inside the rear rotors. The pulverized lining coats the ABS count sensors and the vehicle thinks both rear wheels are turning at different speeds.

That is when automatic anti skid kicks in. The brakes try to stop the spin of the fastest wheel and intermittently applies the brakes.

Remember there are 2 sets of brakes on each rear wheel. The calipers are visible but the drums are concealed as part of the rotor housing.

did you check the brake booster ? how long you use the brake booster? may be have no enough pressure in vacuum brake booster. get more details here for help : http://www.fiverhope.com/
http://www.fiverhope.com/category-67-b0-Brake-booster.html

possible the rear parking brake accidentally set? that can cause hard pedal as well as insuficient vaccum to booster, or bad booster. the fact front brakes are locking up is odd in relation too the rest of your concern. need more info to help you.....

This sounds like the abs system is coming on, this may be due to a bad wheel sensor, the best way to see if the noise is the abs is to remove abs fuse and drive, the abs light will come on but drive to see if noise is gone. by removing the fuse the system will shut down. the way it makes noise when close to a stop means the abs could be the noise, a bad sensor at the wheel would cause this. it looses the signal for a sec or two and the compuetr thinks the wheel is skidding and the rest are moving, so the noise you hear is the abs unit release the wheel. if the abs is the problem then the next step is to have a garage scan the abs module for codes. the codes will tell you where the problem is and which wheel. good day.

this is either a bad bulb or a bad ground. Change brake bulb & check socket too.

go to villager-quest yahoo group for more help

Is it all 4 wheels or just the rear wheels that lock up? If it's just the rear wheels it could be grease from leaking axle seals getting on the lining or brake fluid from leaking wheel cylinders.

If there is no leakage at any place is safe for the liquid is lost from themaster cylinder to the booster

^ Turbo Cars have Lots of Vaccum, Where did you ever get this idea from. I have personally converted 10+ Turbo Buicks to Vac brakes.

Make sure the check valve is okay at the booster. but it does sound like you have a bad booster.
Also, did you change the brake pedal to a Vac brake pedal?
They are not interchangeable.

Also, you should not have drilled the plenum, you can get a vaccum block to replace the plastic one on the top of the plenum with a vac brake port.