Your motor is very strong to pull 150whp with just exhaust.
Most people really won't listen when it comes to N/a KA... I posted up some before/after dynos a couple of years ago with some mods and here was my results.
Run 2 = bone stock KA24de 88,000 miles
Run 7 = blitz realize 3" catback exhaust
Run 14 = 3" Catback + crappy pacesetter header
Sorry, they exported weird and the torque got cut off.
Oh, I just noticed that your motor was rebuilt, that would explain some extra power.