Here is a short report on a CIS upgrade I did a few months ago and it turned out very well so I figured I'd share the results.
If you Don't want to go all the way to megasquirt you can go half way - keep CIS and add computer controlled tune-ability. For less than $300 you can add a wide band controller to your CIS Lambda setup(k-jet). Then you can use your laptop to set the CIS fuel ratio(s) to find the best tune. I've found this to be the best bolt on I've done to my GTI yet. This mod really made all the other upgrades work very well.
You'll need a Innovate MTX-L with O2 sensor controller $199 from DIY Autotune(or similar PLX unit) and about $50 or so in wiring connectors and 2 auto relays. I'm not the first to do this upgrade done back in 2005 by a guy that seems to work at Innovate Motor Sports http://www.innovatemotorsports.com/f...ead.php?t=1520
Gauge fits perfectly in the GTI console gauge pod in place of the redundant clock.
Note where NA motors make the most power(generally speaking more compression will use more fuel). The stock GTI lambda fuel ratio tends to run around 10:1 at WOT. I have found and others confirmed that 13.2 -13.5 is where these VW NA engines make the most power. So the Stock Lamba at WOT is wasting fuel, and not making as much power as it can.