Exhaust is one of the things I’m considering. My biggest concern is since I do a lot of highway miles I don’t want a loud drone. I do like some of the more throaty sounds so if I can get that while not getting a headache on the highway that would be awesome!Driving 2011 Smart Pure in Denver metro area, was getting ~ 39 to 42 MPG on average. Did replace OEM exhaust with Remus center exhaust. It was more compact, less weight, little more sound effects. Did modify OEM intake pipe ass’y that was hard to remove when changing air filter. Simply cut off those three useless chambers & sealed with custom made plastic plugs & screws & epoxy. Each plug made from plastic cutting board/ fitted to opening & sealed with epoxy. Worked great, fix may have improved performance little. Added ScanGauge II to see Coolant temp, RPMs… to make “manual” shifting easier. Air filter was regular paper element in stock filter box.
Using K&N filters should improve any car’s performance, but do not drive in dusty environment!
There are electronic modules that help with engine response and insert at gas pedal harness. Do not remember brand name, but it improved Smart car response somewhat. Do not think this helped gas milage, unlike exhaust & intake mods.