The Baseline Dyno Comparison chart & Calculator

jyhighsky

370z Statistics: 332hp/270tq @ crank

RCZ's 370z: 256 RWHP and 204 WTQ [MUSTANG DYNO]
-0.22891566265060240963855421686747 HP
-0.24444444444444444444444444444444 TQ

STILLEN: 276 RWHP and 227 WTQ
-0.16867469879518072289156626506024 HP
-0.15925925925925925925925925925926 TQ

GT Motorsports: 287 RWHP and 237 WTQ
-0.13554216867469879518072289156627 HP
-0.12222222222222222222222222222222 TQ

DD Motorsports: 285.46 RWHP and 243.40 WTQ
-0.14018072289156626506024096385542 HP
-0.098518518518518518518518518518519 TQ

Injected Performance: 258 HP [MUSTANG DYNO]
-0.22289156626506024096385542168675 HP
TQ unknown

370z dyno: 289 rwhp and 229 rwtq
-0.12951807228915662650602409638554 HP
-0.15185185185185185185185185185185 TQ

17.16% was the average RWHP loss for these SIX cars on their dyno's
15.48% was the average TORQUE loss among FIVE of five cars, for Injected did not provide one.

As mentioned by RCZ, Mustang Dyno's usually reads 8% - 12% LOWER than other dyno's. For example: Dynojet.

Source for dyno numbers: http://www.youtube.com/watch?v=NDQWK1Ny3q0
RCZ's 370Z Journal.