Well the old blow through a straw versus blowing through a toilet paper roll trick would disagree with pipe width equaling air pressure. But I get what you are saying.An smaller pipe won't do that and it's not about pressure it's about exhaust scavenging and the sound. With them both separated completely with no x pipe it may end up sounding like two 3 cylinder engines running. Since the exhaust for each banls are completely separated. 2 inch piping will do just fine .
Engine could be doomed however so I really need to focus on task at hand really last thing I need to worry about is how the exhaust will be ran that's my bad.
I envy you having a shop it appears to work on your stuff I'd be much further along in the process not having to inch worm below the car lol.