My 5spd has been holding up since September last year with 325hp as you'll see in my sig. In that time I've had about 3 or 4 drag strip visits with high rpm launches and a Barbagallo track day. In a couple of weeks I'll be heading up to Racewars for more straight line racing.

Treat the box with some basic respect and there's no reason it can't handle that power. Slip the clutch on launch as opposed to shock loading the driveline, and shift smoothly and swiftly. No need to yank the stick and shock the system with clutch drops. That said, I've stuffed up the launch a couple of times and bashed the box and it is still holding up.

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MY08 WRX 325hp/456nm/18psi E85