How much horsepower does a 2006 STi put to the the ground? Not at the crank..?

Their weak 225 if on a good day, and if your lucky. Look out when an Evo pulls up cause you will get PWNED! lol

That all depends on the Dyno brand that you do the pull on. Ambient temperature takes a toll on turbocharged vehicles, as does the brand/octane of fuel you run.

On the higher side of the scale, they range from 220-230. That is stock.

About the Evo's. It is all in the driver. Do some research.

Correct that it will depend on the dyno. On a proper loading low reading Mustang dyno it might read 240 to 250. That is at a good shop that leaves the dyno calibrated the same for everyone. Some shops will do baseline pulls in a different setting to show that they make high gains with tuning to boost their reputation but that is just sad. On a higher reading Dyno Dynamics or Dynojet it will read 20 to 30 hp higher. On our local dyno at PDXTuning, a stock ST l on a average temp day will read around 240hp & 250tq. with just a turbo back exhaust & a tune, l have seen as high as 310hp & 340tq. Torque gains r even higher on the 08 is with dual AVCS. So all in all, ur question is too hard to answer accurately with all the variables. Just find a reputable Tuner & give them a call to have ur questions answered better. l know the guy is here at PDXTuning r always happy to talk to people so any good shop in ur area should be willing to do the same.