On my 355 Spider i've got the Tubi with no cats option,but I'd just be interested to know under which circumstances is it more likely to spit flames!!? Would it be when I change up near the red line and hear a pop (sometimes a bang or both),or when I accelerate hard then suddenly lift off and hear lots of popping! Anyone any experience on a sure fire way of making it do this? Be simpler if there was a switch on the dash!!