Our model has become un-manageably slow and I need to figure out why. It seems to have gotten a lot worse since putting a lot of stuff onto systems. I noticed that a warning for the default systems will pop up saying something to the effect of "you have over 50 things on this system so we will not do calculations because it will take too long." I don't need revit to do any calculations for me on these systems, is there a way to turn the calculations off on the less-than-50 systems? Or is there anything else I should look into to improve performance related to systems?