Thoughts on this

http://cgi.ebay.com/ebaymotors/25HP-D-BOOST-PERFORMANCE-CHIP-AUDI-S2-S4-S6-V8-Q7-Q8_W0QQcmdZViewItemQQcategoryZ133193QQihZ002QQitemZ120226975633QQrdZ1QQsspagenameZWDVW

Its a very bad idea.  It tries to manipulate iat's so the timing stays higher when it should be dropped to prevent damage to the engine.

yeah it doesn't sit well with me either. Hey have you seen the do it yourself air/fuel gauges. I found it pretty interesting. I have been thinking of building 1 and matching it's values to vag-com check out the link below
 
 
 http://www.redline.lt/magazine/spec-features/article/article/17/1/

You are going to need a real wbo2 for it to be accurate.  If you want to monitor a/f, get a real kit with a gauge.  They are about $300

cool thanks cincy.