Hey bud, any progress with the shuddering, it sounds very similar to the problem i have, when warmed it gives off a random shudder, i have tried replacing both the coil packs and plugs, to no avail, i took it to Dan (3lite 32) and we hooked up the lap top and went for a run, and he said that the car is running fine, (initially it was for a different problem which has turned out to be my tyres which were wearing unevenly due to needing an alignment etc..)
Anyway, with the laptop hooked up, i pulled into the driveway, it has a small slope and so im parked on the slope, and suddenly we notice this misfire like shudder occurring, quite strongly i might add but the laptop shows no problems, ecu had no error codes either, i rolled the car back onto the flat section and the feeling disappeared for the most part but still retained that gentle shudder here and there.
(this was all on a cold night, warmed up car)
So, all that said i think i have the same problem as you, and Dan had no idea what is going on with it, so im very interested to see what you come up with
Steve