Been running 5psi on my somewhat of a GReddy kit for over 2 1/2 years with all kinds of hacks and bad tuning, until I found and got better with tuning softwares out there. 4 Months ago I turned the boost up to 10psi after an entire exhaust system upgrade. Within the next month I will be getting some dyno time in and turning the boost up to 15psi.
Reason for the ramble, even with my period of poor tuning I have been running boost for just about 3 years and the compression test of said motor as of 2/1/08 is 210 across the board. These motors can take abuse especially with proper tuning and power output for said components.