It could also be a fueling or ignition problem. I had a similar problem where it was turning the downpipe and converter cherry red. It ended up being a bad tps and a weak coilpack. I guess it had the fueling so messed up that it was driving the egt's that high. Anyway, it didn't boost right and when it did it would pop in the upper rpm's. If your car is running rich or if it has an exhaust or vaccum leak will effect the boost too. I can't explain the boost gauge except that it is electrical so it may be a bad ground or something.
Do you have a scan tool? Any readings?