Think*

 

I don't know if cutting the spring would work but the computer will definitely let you have more boost without chipping it. I saw the VAGcom read out of a guy with a K04 in his peaking 18.5psi in third gear with a stock N75 chip no reflash.

 

from what Ive seen and worked on I don't think thats really likely (not saying it isn't, it could be possable) just saying from what I've seen with working with Revo tuning getting much out of a K03 is pretty diffecult. It's just cutting the spring or putting a stiffer one I believe wouldn't do anything with the computer controling the boost. The K04 on the other hand is a whole nother beast in itself :P I really haven't messed with them (not many people actually upgrade to them here.They always talk about it never do so I've only seen like one I think XD