99 Bonneville has issues with low brake pedal. Has since I bought the car with 40000 miles. It now has 64000 on it. Brake pedal is extremely close to floor and has slow reaction to pedal travel. Brake pads almost new. New rear wheel cylinders. New MC. System completely bled. Could this car have had the wrong booster from the get go. Have owned 2 other Bonnevilles, a 94 & 97, and the brake pedal feel was much better. I know all cars are different, but something is not right. Any ideas. Thanks

Check for a vacuum leak at the booster. Are there any signs you have a vacuum leak anywhere, such as rough idle?

I would check the adjustment of the rear brakes if there not adjusted enough it could cause the pedal to be low. Also i would try bleeding them again. There might have been air trapped in the abs when they where bleed.

Pump the brake pedal several times and see if it comes up off the floor, or gets firmer. If it does that is a sure sign you still have air in the system and that you need to bleed it some more.