I purchased the 99% membrane and a new gauge. The water faucet in my basement is an irrigation faucet, when I tested the RO/DI unit I had the faucet knob opened to the max point. I'm sure that affected my TDS since there was probably too much water flowing in at once.
I doubt it. Not sure what your irrigation faucet is set at, put when I do a google search it says most are set in the 50 to 60psi range, which is the normal water pressure for most people. I've known people to run their ro systems at 120psi. I believe more pressure actually helps the system be more efficient, the problem is the joints are not rated to go much higher than 120psi.