My GT35/40 on the street starts making some boost at about 2800rpm, Full boost is between 32000-3600RPM depending on which gear.
4th and 5th gear will make full boost at 3200-3400RPM, 1st and 2nd gears are too hard to tell (Wheelspin, revs too quick).
3rd gear (with NEW tyres otherwise it wheelspins aswell) has a little less load on the engine and makes full boost at 3400-3600RPM.