ATX - replace passive PFC to active
Do a test run. The active PFC board, the big capacitors and a passive load. If your board is self-contained (=needs nothing from the PSU) you can easily find how high voltage you get into your capacitors with different loads. The highest value must not exceed the peak mains voltage. You need a meter that can show peak voltages. An oscilloscope is a kind of russian roulette due the signal ground connection. You should have isolation transformers and be agilently conscious on what you do to keep the mains voltage out of your fingers and the oscilloscope input.