Update, since replacing the engine and transmission entirely I haven't had the problem anymore- I transferred the 150 mile old Fidanza flywheel and OEM clutch/slave/pressure plate I had just put on the old setup over to the new one and did nothing else, so I am still lost for why it was happening in the first place. It happened with the 145k engine, transmission, and original clutch, flywheel, and slave on it and it happened with all new clutch, plate, flywheel, and slave, but not now with the same new parts bolted to a younger engine and transmission. Weird. I'd think I hadn't bled all the air out, except that it was happening on the old engine before and after in exactly the same circumstances and in the same way. I'm just glad it stopped now. lol