Current Revision = 1.0
Also Check out thesuicidaleggroll's turbo calculator. Will help you set realistic goals for your car.
And if you don't know what the input variables mean, you should probably do some more reading before you start tuning. It's a good test.
If you're having trouble viewing, try it in firefox and ie. It's a google sight and I personally never had any problems with it but others have. Might be from using other browsers. If it doesn't work on major browsers, we'll figure out another host somewhere. Also, if your work filters block google docs (as mine do) you can't click the "view" button. You have to download the document.
UPDATE 10/1/2010: Rewrote some of the wastegate part and cleaned up some wording here and there.
UPDATE 08/12/2009: Just added the references as Tea Cups requested. Info stayed basically the same.
UPDATE 03/31/09: Version 0.5 includes Corrections made as suggested by Tea Cups
UPDATE 03/26/09: a .doc version of this guide. First version .doc version was 0.3
thanks to WideBoy, we now have a great .doc version of this guide. I've been working with him for the last couple of weeks to get it done. We did a great job revising the info here and I would say the .doc verison is superior to these posts. We worked on clearing up things that may seem confusing as well as added some info + revised some tuning techniques to be more clear.