I usually don't let it get over 1450 degrees (manifold temp). I have seen higher for VERY short bursts, but I let off if it does. I've heard many stories of 1200-1300 sustained for hours and hours straight and no issues.
It's funny though. If you take a stock a$$ D-Max with NO programming, install a pyro, and hold your foot to the floor while towing...your EGT's will peg the effin gauge past 1600 degrees. So 1450-1500 for short intervals is nothing for these motors.