Join Date: Dec 2009
Location: Austin, TX
Ferrari Life Posts: 1,219
I have only ever used the Hyperflow cats on Ferraris, so I can't speak for the Nuvolaris. If the cat core is spec'd correctly, you will not get SDL's or CEL's. You will probably gain 10HP or so. Engine bay temps should decrease slightly too. You won't experience any dips anywhere with proper cats. The reduction in backpressure will improve HP/TQ across the whole range.
A tune is not "necessary" in most cases. However, it is ideal to have the AFR's checked and verified on chassis dyno and have the ECU tuned accordingly if adjustments are needed. I will say that you stand to improve the longevity of the high flow cats by having the ECU's tuned. These cars run very rich maps, particularly @ WOT and the excess in raw fuel will accelerate cat core degradation. If you have the ECU tuned and the AFR leaned out slightly for maximum HP/TQ, there will be less excessive fuel running through the exhaust, thus increasing the cat cores life span.