It seems silly that when you go to upgrade your turbo to stage three or four, it shows off a nice pic of a dump valve, now for a beginner to the game notices this pic, and needs like 42,000 for it then its something worth saving for until...
It doesn't make a change to the car what-so-ever!
GT4 is a class game, and i am not faulting it, it would just be better if you heard the release!
also, the dude "it seems silly" you obviosuly havent experienced driving along the road watching a scooby or an evo tear it up with a dump valve.
When you see a ragged up car on the road, the first thing you look at is its body kit :- splitters, bonnet, side skirts and spoiler, or in an Evo's perspective, the massive beast of an Intercooler!
The first thing you listen for is the dump valve, and if you don't hear it you hear the whistle of a turbo and a power exhaust, which in my case are as common as muck these days!
Kev.