Phil, this probably doesnt help you any.......lol......but both of my cars have the powerplates, and they are NOT drilled. However, after reading this, Im thinking about drilling out the one in the ttype since a get a lot of part throttle knock/passing on the highway knock. But, most of that (from my testing) has been from crappy 91 octane gas in Pittsburg.
Anyone else have any further information on drilling vs not drilling. You got me thinking about the EGR operation at cruising speeds. The EGR does cool off the combustion chamber a bit....hmmmmm