Is-there-a-limit-to-how-many-threads-an-extension-can-run-in-parallel

I'm working on an extension that calls strategyrunner potentially many times. Using TPL (task parallel library), I'm trying to run multiple threads in parallel. It seems like regardless of how many threads I create, I can't seem to get the CPU utilization higher than around 30-40%.

Is there a limit to how many threads an extension can run in parallel?

Thank you,
Paul