Hello everyone

I have a 2003 Z06 that I have been fighting a soft brake pedal on after going to VIR and CMP. It has Wilwood front calipers on stock size rotors and stock rear brakes running Carbotech pads.

At CMP the pedal started going long/soft, but coming back after cooling. Then it went soft and didn’t come back. I figured I boiled the brake fluid so packed it up and went home.

While at home I decided to do some preventative maintenance and upgrade the brake fluid from ATE to Castrol SRF. I replaced the front hoses, had to fix the front left hard line from a previous stripped tube nut that was fixed to get by. That line was removed from the ABS unit so I could redo the bubble flare on the bench. I also replaced the master cylinder thinking it could be contributing to the soft pedal (it was bench bled before install). I bled the system several times, but couldn’t get a good pedal. did the ABS bleed a few times, including driving it down the road and braking until the ABS activated then rebled. I can’t find any leaks and am not getting any more air from the system.

I know a soft pedal isn’t normally attributed to a booster issue, but could be a possibility, so I replaced that. It felt good after doing this, but a mile or so up the road it started dragging the brakes pretty bad basically locking them up. I managed to get the car home and took the master off. It’s obvious that the booster pushrod is pushing the master cylinder and not allowing it to release fully, so the pushrod is too long. I compared it with the pushrod from the old booster and they are different, picture below. Swapped in the old push rod, but no improvement.

doing research it seems the 2009-2013 booster is a replacement, but only if the master is used as well. I don’t know wha the difference is here.

Is it possible I have a mismatch of parts?
is there any adjustment in this system? I could cut the pushrod shorter, but would like some advice from the experts first. I would rather not take the booster back out, it’s a pan to get to.

thanks for any help

Edit: I checked the part numbers and they should fit. Master cylinder is AC Delco 18M2441 and Duralast (same part number as Cardone) 5471263. Say they fit 1997-2004 and 1997-2008 respectively.