Hard brake pedal on panic stop only.

Hi all and thanks in advance for your help with this. I’m going to try to list everything that may have resulted in this issue to help you help me.

2007 Honda Civic EX with a rock hard brake pedal ONLY on a panic stop.

What has been done:
Brake job w/ brake bleed using one man bottle method. The brake fluid was old! Had not been replaced in a long time. I screwed up and let air into the master cylinder (the reservoir had a stain on it that looked like the fluid level but it was LIES!) I knew that I had messed up when I got the spongy pedal feeling. Did not have time to rebleed so I took it my local shop and asked them to bleed it. (I heard the mechanic let out a strangled cry as he realized that I had worked on it and wanted them to fix it – poor guy, but I did not screw up THAT badly.)
They bled it with a vacuum bleeder and the sponginess is all better.

I did a good job on the brakes and they are smooth as glass and make no noises. I have performed basic function checks like pumping up the pedal with the car off and it is a rock for over 3 mins – no movement. The pedal sinks appropriately when the car is turned on. The pedal maintains it’s height with the car on and light pressure. It does sink to the floor with a little more than light pressure but it does not just sink or fade away on it’s own when braking normally, just if I put extra pressure on it.

Braking feels good except for one thing. Rock hard pedal on a panic stop, although the brakes seem to work ok but maybe not as good as they have at their best, used to be able to kick in ABS easily, but I do have Akebono’s on that are a little softer than the last pads.

The two places I’m thinking of checking is the PCV valve and the booster. What say you fine gentlemen!?