Steve,
very useful to have a recommendation for inexpensive alternative parts:
"cheap Chinese headers from (you probably know the ones from Texas)"
Don't be shy, please tell us the name of the company?
Was it this guy?
Top Speed Pro 1 Performance
Porsche Boxster 2 5L 97 99 Performance Exhaust Header Headers Long Tube Runner | eBay
Steve confirms "yes" & they fit and have the O2 sensor holes.