I've replaced the master cylinder (three times), the metering valve (twice), the brake booster, the proportioning valve, new stainless brake lines front-to-back, new calipers, rotors, pads, drums, shoes, hardware front & back, brake warning switch (3 times), rear brake hose & passenger's brake hose. Only older part is left is the driver front brake hose & I wasn't getting fluid out of the passenger caliper, so the driver's hose isn't it. Master cylinder was bench bled + later bled on the car with the hoses (when I questioned my bench bleed).
Last night my wife pumped the brakes and I found a leak near the proportioning valve where the line between the proportioning valve & metering valve connect to each other at the end, so I have at least one more thing to try. The last leak(s) I fixed two days ago were this line & the one that comes down from the back of the master cylinder to the metering valve. It "seems" like with these stainless lines they start to leak at the ends if you connect/disconnect them a few times. I've also been unable to double flare the SS line with my flare tool (too hard & line slips out of grips). Since it doesn't look like Inline Tubes sells partial SS kits, I resorted to compression unions & mild steel line to fix the leaking half of the line(s). Now the "good SS half" of the line I mentioned is leaking too, so I will see if I can replace the whole line with mild steel. I have one more new proportioning valve I guess I could try too if it's the female half of that connection that's causing the leak.
