Here's the "problem".

You upgrade to a K04 for better performance. GIAC's "standard" K04 software using the 5 bar fpr (for 2001 cars) has a problem with the throttlebody closing under full boost at around 5000 rpm. You can keep the K03 software with the K04, but not really worth it, or upgrade to the GIAC Hammer file which requires all the stuff I listed.

Apparently this is a problem with 2001 cars only. So, if you have another year, maybe software is all you need.

 

I've heard about this problem but I thought the hammer file fixed it with just bigger injectors.

 

The Hammer file did fix it, but it requires more than just injectors. It requires the MAF, stock 4 bar fpr, FMIC (recommended) and exhaust (recommended).

 

Interesting.. Why does it need 4 bar fpr instead of 5?

 

That issue was only with the 01's thought right? So, if you don't require the hammer file to fix that one issue then you don't need the additional toys

 

The Hammer file uses bigger injectors. They require less fuel pressure.

I think the throttle body issue started with the DBW '00 A4 and I have only heard about this problem on GIAC chipped cars. Usually on K04 equipped cars but, some people are having this problem with K03s.