Cheers mate, my biggest concern was AFR's getting too high and hitting R&R, as well as wastegate creep/boost spike.
I bought and installed a Venom 400 Series 100cpsi cat and took it for a drive this morning. Ambient temps were around 16 degrees and I did a few 3rd gear pulls to load the engine up and it didn't have any trace of flat spots or ignition pull. Having said that, it didn't perform much differently to the old cat, maybe a slight increase in response, but that could just be placebo. Does sound a bit better though
So going by the fact that it drives fine with the new cat, I can drive it 'as-is' with no worries until I get a tune? I'm a uni student/work part time so it could realistically be months before I get the money for one. I just don't want to damage this engine in any way haha