My bike used to backfire if I upshifted anywhere past 10-11k rpm. Valve clearances fixed that.
But on topic: I have a 800w 10" subwoofer in my car but I'm thinking of downsizing to one or two 8"s (200w I think). I've got all three and I'm about to build two boxes for the 8s. Just gotta buy amps. But I want to decide if one low power 8" is "enough" for my small car before I buy house or car amps.