Question about catless downpipe

[Martynas]

Hello everyone, I have bough my Mazda with both catalyst converters tanks empty and now I am running high load tune.
I wanted to ask if I will encounter any problems or downsides, because on tune description it says that stock downpipe is required?

[Ugnius @ VersaTune]

A catless downpipe will have less backpressure and the turbocharger will spin up faster. As a result it may overshoot the boost targets. The ECU will correct that eventually, but you might see boost spikes on turbo spoolup.

[mituc]

Also, that faster spool maybe problematic without upgrade fuel pump internals because there will be moments when the fuelling system simply can-t keep up with the fuel demand. So you should also consider that.