exhaust back-pressure and break in question...

[Garrett]

Does exhaust back-pressure influence how effective an engine break-in process is?

I have a race in which I may run an open exhaust off of the stock heat exchangers, but I have just 500 miles on my complete engine rebuild (a 3.6 in a C4 TurboLook). Is it better if I run my usual exhaust system that provides "more than open-exhaust" pressure? The system I'd run is the stock heat exchangers, cat bypass, hollowed out primary muffler, and secondary bypass. Should I not use the open exhaust which adds a primary bypass pipe to the above equation??? Just curious from the knowledgeable minds here on Pelican

Thank you!