I didn't mean to hammer you about efficency...
I apologize if it came through that way.
But I'm going to beat you up some more...
Actually the Compressor status call takes just as much time as the Start/Stop vi's, possibly longer since it will wait up to 100ms for the status from the other task before returning. This while it's being called from what's supposed to be a 20ms vi. The Start/Stop vi's return immediately.
I don't think the compressor part is a CPU issue. I think it's a sluggish loop issue. Anything longer then 100ms will trip the Safety vi's, which isn't a bad thing as it's notifying you that there's a timing problem.
You can probably move that LED to a slower periodic check. A quarter second is probably unnoticable to the driver.
If you want to get rid of the refnum altogether, even the use of global overhead, you can put the whole kit and kaboodle into Periodic Tasks.
Have you analyzed the CPU usage with the System Manager to help isolate the CPU hogs?
Have you tried using the Elapsed Time vi under Project Manager->Support Code to identify the loop piglets?
Can't comment on your other motor output calls.
Those could be due to other reasons, such as, an unrestrained loop that does make it a CPU drain.