Can you be more specific about how exactly these modules (are these really blocks?) are activated or deactivated for a particular run?
If these blocks receive data and do any operations, including data logging, they can influence the step size of the solver if using a variable step solver.
What does "do not pass it back to the simulation" mean? The blocks are part of the simulation. Maybe that means the blocks don't pass data back into the loop?
If the block sample time is set to a large number (w/o a sample time offset) I'm pretty sure the block will still execute at t = 0, though I'm not sure if/how that can affect the subsequent time steps.
