I was thinking that you may have switched over to a puck/carbon type clutch, which can occasionally have such an effect because they are so grippy. Not sure if all organic Exedy's have the same traits, but the Stage I heavy duty Exedy on my SC is also very grippy, and doesn't allow for virtually any slip as it engages. I have to make sure that I keep the revs up a little when cold to avoid issues. It gets better as the engine warms up. It also helps to make sure the low rpm/idle system is operating at peak efficiency, or else it can add to the shudder. A well tuned car in these cases makes a big difference. Additionally, I have stiffer than stock engine mounts, plus the whole intercooler setup on mine reduces engine rocking, and those items combined add up to a greater possibility of 1st gear shudder with a grippy type clutch, as it prevents the engine from rocking as the clutch tries to engage, otherwise absorbing some of the shock.