TOGA1116

I have the exact problem as dough. I've replace the master cylinder, hydroboost (twice), front calipers, pads all around, AND i replaced the ABS module & pump (with a salvaged one). I thought the ABS module would be the one to fix it, but it wasn't. It did the same exact thing after replacing it. I haven't done the rod length thing because 1) I've never messed with the rod 2) Why would it do it intermittently and infrequently? Any other suggestions folks?? I've had it at two different mechanics and they're both at a loss.