Replace leaking fuel pump. Yikes!!

[mudski]

Nope. No boost gauge.
I've only had it for a few months and as far as I am aware no mods have been done to the motor.
Is there any way to check the boost without a gauge?

No, a boost gauge can be temporarily put in though. Reason for my asking, is poor performance can be due to a leaking intercooler. Sometimes the leak is not so prevalent whilst not under load and normal driving so its no so noticeable. If you run a boost gauge you can monitor boost levels and see whats going on.
So have a look at the intercooler, best to remove the plastic engine cover, if the end tanks are crimped to the core of the cooler, like a genuine radiator is, its the original intercooler. If it is, have a look and check to see if there is any oil deposits on the core of the intercooler. Particularly when the crimps are. Its best to check the bottom side too. If you see any oil wet spots, thats a very high probability that the intercooler is leaking.

So, what damage can be had from a leaking intercooler? On a stock system where boost is controlled via the factory control solenoid, the turbo will have to work harder to compensate for the boost loss. So extra fuel will be used and extra, unnecessary wear and tear on the turbo.