It does sound like you are over running the stock "boost limit". On the 03 models, the factory boost limit is 230 load up to 3500 rpm and 225 load from 4000 and up.

4th and 5th gear should hit fuel cut a little sooner since the turbo will spool quicker. wot at 3K in 4th will probably hit fuel cut by 3750 in 4th. wot at 4k will probably hit fuel cut by 4500 ish in 4th.

basically, as soon as you hit full boost for more than 1 second (defualt boost cut delay timer).