ive noticed on a picture of a prodrive sports cat that the bellmouth has a wall running through the middle.is this any better/worse than the 'wall free' open bellmouths on aftermarket sports cats that im thinking of buying?

 

It would hardly give ant noticeable diffeerence in my opinion.
I had a MY03 STI remapped with the usual mods and achieved 336/320 with the Prodrive sports cat d/p.

Cars with similar decatted systems produce slightly less or slightly more but there isn't a noticeable trend.

Stick with legal.

 

cheers bob

 

The idea of the divider it to stop the exhaust gas from the wastegate creating turbulence in the main exhaust stream from the turbine, and hence slowing the gas down.

I suspect any gains from having this would be insignificant.

 

earlier prodrive cats had two pipes blenfing into the downpipe whereas later ones had a bellmouth with a divider, doubt there would be any noticeable difference between them. I have a 2005 sti downpipe on my wrx and would rather have this than a cheaper alternative, it flew through the mot with no issues at all.