I owned a 2015 sti for a few months before it got totalled. It was full stage 2 with only the turbo being stock and that was going to be swapped soon. After loosing it I got my z and loveee it. Sti's are fun and handle great but the z is always more fun for me. Sure the sti was a tad bit faster but my z is still stock and the sti is no fun until you drop a few grand in it plus they are always going go have motor troubles. I watched my buddys sti with a 1 year old short block from subaru blow a ringland on a downshift.
