After doing the drill hole and piercing of the trans I got a further 30k kilometres out of it before solenoid 2 totally failed (unrelated to the piercing). I ran a Magnefine filter inline with one of the trans cooler hoses and it was great. Then the heater core failed, then the ABS system was totall...

Thanks! I forgot: you had an external filter, correct? I have a feeling that at the moment my external filter plays a part in the problem. My theory is the internal is clogged, so pressure is reduced. And then, the external filter adds another drop to the pressure - especially as I placed it where ...