Interesting change on the stacks/tubes KansasZ.
We did a similar mod back in the early 80's on four cylinder bikes (pre Ninja & GSRX ie GPz & GS-ES bikes). We pulled the airbox entirely and put on curved 'tubes' with pod filters on the end. I can't say for sure how much extra power we made, or didn't make (my bike had adjustable Canadian needles - USA needles were fixed), but the bikes that did this were among the fastest in Las Vegas at the time. Wonderful 4 barrel automobile intake drone. My '83 GS750ES w/Action Fours extra plate clutch, would clean up on everything except a GPz 750 national record holder.
RB Racing headers and intake tubes, and tuned/jetting by 'Crazy Ed' Malkewecz (spelling?-sorry my old friend Ed, where are you?) ...National record production drag bikes with that tuning on roadracers... Fun sheet!
Maybe you have knowledge of Crazy Ed?
Your bike deserves some dyno time to see if your stacks/tubes swap really does what its supposed to do. I'd be very curious.
I listened yesterday, just to see... putting around my area, and I can still hear my transmission gear train whine when cruising about with my header. But when I'm on it... its all pipe!!