i was reading on a celica forum that the 1zz-fe is a hard motor to build NA. without increasing the displacement (bored out) and by just building the head alone to its maximum potential you can get only 160-180 flywheel hp. but don't take my word, i'm just recalling what i read in a celica forum. one more time: 160-180 flywheel hp NA. no turbos or displacement changes.