most n/a motors dont make 500hp. much less i was assuming we were talking 4 cylinders here, and ive yet to see a 500whp n/a 4 cylinder.

and its not ur ecu limiting boost in first... its first gear limiting boost boost is basically a product of load. if an engine is allowed to rev freely its not really producing much in the way of torque {notice cars never build boost when u just rev the engine, or very little at least} first gear makes the engines job alot easier and it doesnt happen for very long {until u shift to 2nd} most turbo cars dont have the time, or produce enough exhaust energy to spool the turbo in the short and basically easy going 1st gear. most cars will see slightly higher boost on the highway, usually in the way of boost creep.

on dyno's its different. if you have the throttle wide open, and the rollers are providing the load u can and will see max boost in just about every gear. still 1st can be a little too low to develop max boost. allbeit true running in 4th is the most accurate {closest to 1:1 ratio through the tranny} the numbers given in any other gear are going to be accurate as far as consistent. but will not show the exact same power readings as done in 4th gear pulls on teh same car. you will notice alot of people that make constant pulls {heavy tuning sessions} on the dyno will often do so in 3rd gear. the event takes less time to happen so u save engine wear {a little} , and dyno time.