I got a full yosh system, no PC, runs a little rich, but no problems. A PC will definitely make it run stronger, but I've put 3k on mine since I've had it, (8k total on bike) without issues.
I have a Yosh Duplex system and a PCIII, but i used to bike for almost a month without the PC when it was sent to Dynojet for investigation/replacement (had some firing problems with it).
Honestly, i did not see a difference AT ALL with or without the PC. Like said before, you're mixture wont be perfect but it wont affect to the point as to cause damage.
The PC is really to fine tune everything together and get the most out of your setup.
My ,02$