If you are wanting to put more than 300bhp in the ED30 imo you need to look at the engine mounts being uprated, very least the dog bone.If you trackday, 1/4 mile then i would uprate the others too the best scenario adding a quaffe/pelq dif then i think you can handle the 330bhp.
Tuners can add silly amounts of bhp to their cars as they are advertising cars, parts cheap and when it goes wrong they can fix it at a better price than joe public could.They keep them for a while then sell them on.When the mk6 comes out the likes of regal, awesome will be first in the Q.
when the 2.0 tfsi first came out tuners advised no need to go upto 3" system the 2.75" was adequate enough. Now its the reverse.