in response to the smart car upgrade..... yeah, definetly get a tuner. perhaps a cowl induction hood to draw air from the low pressure area at the base of the windshield routed to a cold air intake. for exhaust, you might want to step up to a 3" pipe for better breathing, and to let everybody hear all that power!!!!! better make it 2 3" pipes, with a crossover to balance out the exhaust. wouldnt want 1 cylinder to be running richer than the other
as far as towing with a miata, did you know they make a kit that allows you to install a 5.0 ford (302 for us old timers) into a miata? they even make a kit for swapping in a chevy ls series motor (think corvette). looks to be fairly straight forward with only minor fab work involved. pics look like it belongs there.