That's the one.
I agree that the inlet flow is via the red arrow, but that's about where it ends for me. If you numbered the chambers 1-5 (working left to right), surely the gas would end up in chamber '2' initially?
Then it would swell in this before either moving into the centre where it would collide and equalize with the gases from the other bank (pipe where green arrow starts) or be pushed through the unmarked tube at the front and out into chamber '5' (or chamber '1') for flows from the other bank.
Either way the gases end up back in either 1 or 5 and pass down a pipe you can't really see in the picture (mustard arrow) and out of the tail pipes in chamber '3'
As i see it chamber '3' is hardly used - so drilling holes through the inside wall of this pipes can't really improve flow or change the should in the way a PSE does?
Be interesting to know when the change in design occurred between the 2001 cutaway and Johnny D's 2003 example. But again drilling these pipes in the 2003 doesn't look like it would help? The pipes run pretty straight with only an equalizer pipe in between.
There was another hack out there that suggested drilling out the inlet pipe (inside chamber '1' and '5') reducing the amount of chambers the gas travels through. This would kind of work on the 2001 system but not the 2003.
Ha Ha
not really sure why I'm that concerned but I'm just one of those guys who wants to know why. I have i 2002 S - so its sitting somewhere in between the two models - no drilling for me - i really like the sound of a SCART system i heard on Youtube but that kinf of sound comes at a price. French company i believe.