Hello Lucas, sorry I wasn't referring to a conventional o-ring, but something metallic like you would use to o-ring a head to a block.
Here's some new technology that I understand works very well for a drag race team who are running over 45psi boost on a Japanese motor:
Helicoflex. They have o-ringed their head to the block with this gas filled SS o-ring and it works well, and is also reusable because it does not deform permanently after installation, but will retain its original shape.
The A/R ratio I was referring to is illustrated in the photo below. Turbos with a small A/R ratio spool up very quickly, but are also more restrictive to the exhaust system.