Mr.R wroteIf it were mine I'd cut the bottom square plate off to see what's been done inside the mod.
The mod' was pretty common back in the day, it involved welding a piece inside the void that directed the gas from both downpipes towards the cans.
It's quite easy to do if you're able/any good at fabrication?
Steve R
Nothing inside , i recon ill cut it open and insert a directional feature