I wouldn't change it at all, unless you have to. I would install a boost
pressure gauge and maybe an EGT gauge as well. They are inexpensive and
chances of the stock turbo overpumping is slim to none, considering how
conservative the factories are.
Steve

"GriffithBuilt" wrote in message
ups.com...
I have an old exhaust manifold for turbocharging a vintage BMW and I'm
running into a trivial difficulty with the wastegate flange. It's a
two bolt flange with a 22mm hole in the middle for the wastegate valve
to seat against. It's a leeetle small and I'm worried about boost
creep (engine getting higher psi than intended due to bad flow out the
wastegate). So I need to modify the circular hole to be around 32-38mm
in diamter instead of 22. Options obviously are use a flycutter to
machine it out or simply use an air powered die grinder (low tq, less
chance of mangling it) to grind it out after stenciling a template over
the existing hole.

Thanks for your time,

Jason