maybe some of these things may help.
1. mushy pucks can be a symptom of underdosing - not having enough coffee in the puck. try the collapse method where you tap the portafilter down on the bench/knockbox whatever to allows space for more coffee in the pf. grinding a little coarser, may help too.
2. with clumping, some people like to do the weiss distribution method which is basically finding a needle or the like to stir the grinds in the pf before distributing and tamping. helps to break up clumps.
3. where are the pinholes? in the middle or the sides of the puck? if at the side, then this might be a tamping/tamper issue. you using the nsew technique indicates to me that perhaps your tamper is not a snug fit for your portafilter. if theres too much space between the sides of your tamper and the basket then you may not be getting good side adhesion, and having the water travel down the sides of the basket.
4. play with how you tamp - hard, soft, straight down with or without a polish, nsew, one tamp, two tamps and see what works for you and your machine.
maybe some em6910 can shed some machine specific light down upon you.