Blank off the EGR first, for such a low cost tweak the results are pretty good apparently - costs about a tenner for a kit from e-blag I think.
If that doesn't do it for you, then think about increasing the fueling, more boost on a 300 without changing the intercooler, while it might look impressive on the boost gauge probably won't increase the performance a huge amount. Of course, change the intercooler and you'll notice a difference anyway, but this is where tuning them starts to get expensive.
If you're going to DIY tune it, you need some patience, an eye for detail and a methodical approach. If you don't have those, or even any one of those, you're probably better off leaving it to someone who does
Always a good idea to remember that 'the faster you go, the faster things will wear out'