They are known to have a bad exhaust floor chamfer. It has to be cleaned up.
It’s been found but I’m unsure if the newer offerings have improved the flaw.
It is not great that a product should have a flaw and still be available. Many that purchase don’t have the ability to find or fix.
Don’t mean to be a Richard Cranium, but you do get what you pay for. A new OEM 660 cylinder ported by a pro is a $500 item. At 1/5th the cost, one takes their chances.
I’d contact Bruce @HL supply. He is an awesome guy and I’m sure you’ll be pleasantly surprised at what happens.