What shoud my EGT guage read.........

[SideSlip]

...........at wide open throttle and 15 psi?

 

[subtlt]

Depends where you're thermocouple is mounted. Seems that if it's near the O2 sensor, folks are shooting for 1550? Do a search and see...

 

[azgn]

it should read wherever your car runs best without knock......there is no magic number, but you'll find it if you do a little tuning.....if you start out rich, you will get false high readings...generally, most guys are happy around 1500-1600 (I doubt you'll see that at 15 lbs boost)

 

[TurboDave]

As has been hinted at, there's no magic number. Depends on where the sensor is:
Let's assume it's near the O2 sensor, still too many variables.
Lean, rich, timing, etc.

At that boost level, you might be lucky to see much over 1450-1500, assuming a fast reacting probe.