Well....on a non-forced induction motor, there's not a 'whole lot left on the bone' for easy bolt on upgrades.
For any motor (in essence, an air pump), upgraded air intakes and filters are always the start. Likewise, catback exhaust is the 'mirror upgrade' to get the extra coming in, out quicker. Not not abouf downpipes and cats...not that far yet.
I'm told a Pedal Commander can add a bit more pep for this platform, so for a few hundred bucks, ill probably grab one and see.
It's my opinion, with a very short experience, just generally speaking, the win on the ILX platfirm comes with these cars being small, light and reliable....add nimble (SUSPENSION AND WHEEL GUYS CHIME IN) and you've got something.