I'm pretty sure the 850 R models (R and T5R) limited

max boost for about 10 seconds then revert to the same

boost as the "plain" turbo models. I guess they figured

more then 10 seconds would stress the engine (but by then

you should be pushing 80 MPH from a standing start).

The 70 series ECUs are more sophisticated and allow the

max power (236 to 260 HP depending on model, as I recall)

as long as engine temp, pinging, etc. are all within bounds.

Now, the 70s could end up the same as the 850 R models

since 10 seconds of full boost could build up enough heat

to cause the ECU to back off just like the 850s do. Heck,

on a hot day you might not even get 10 seconds.